A deep attraction from the start, followed by a shared stumble at the first turn. Each gives the other what they need deep down, then leaves them alone where they need help most.
You can recognize this relationship by its effect before you know its name. One person finds in another something they had been looking for without knowing what to call it: a way of seeing life that quiets an old anxiety, a presence that makes what felt heavy seem lighter. They feel drawn to this person in a way that is hard to explain. Then a situation calls for something quite different—an honest emotional conversation, careful accounting, a firm decision, or care for someone who is ill—and the two discover that they are equally helpless. Each had been waiting for the other to take care of it.
This relationship is called Semi-duality. It pairs two types from neighboring quadras. They share a rhythm—both are decisive or both flexible—but differ in energy orientation and in the angle that shapes each person’s core. There are eight pairs. Semi-duality is sometimes called “incomplete duality,” which is half right but mistaken about which half is incomplete.
The strange thing is that the deepest part of the relationship is completely sound, while the simplest part is disabled. The part that can take years to find in other relationships—the experience of someone whose presence gives you what you lack deep down—is here from the beginning. But everyday support—who handles what I cannot, who protects me when I am embarrassed—is missing. Imagine two people hearing the same music and dancing to it, then stepping on each other’s feet every time they turn. This image—one melody and stumbling steps—will return whenever it helps explain what seems unusual about the relationship.
The nature of the relation
Semi-duality rests on one idea: the two people meet completely at a deep level and part ways in the practical details that protect daily life. This involves the eight aspects of personality explained in “How to Read the Relationship Pages.” Every relationship is a particular way those aspects meet. In Semi-duality, each person’s core meets the other’s deep need, as in the closest and calmest relationships, while their tools and vulnerable points do not complement one another.
What sets this relationship apart is that each person’s hidden need is reached by their partner’s core—what the partner lives rather than consciously presents. The contribution arrives as an atmosphere, not an intervention, and this is the source of the attraction. What each person presents falls on the other’s quiet skill: a field both are good at, but one person uses openly as their approach while the other uses it in the background without talking about it. Their vulnerable points remain unprotected: what hurts one person is exactly what excites the other, and the other is not good at it.
They meet easily at a deep level, then stumble together on the surface.
What One Person Lives Enchants the Other
What meets here: each person’s core with the other’s hidden need.
Each person’s core flows into the other, just as it does in the closest and calmest relationships, so the effect is early and clear: a deep attraction that is hard to explain. Someone who needs a wider horizon finds a partner who naturally sees possibilities and feels the world expand. Someone who needs reassurance and a calm rhythm finds a partner who naturally attends to the body and comfort and feels the days become manageable. Someone who needs a clear moral compass finds a partner whose life is guided by appreciation of people and loyalty, and feels reassured about those around them. In each case, the partner does not offer a particular thing that can be pointed to; they simply live in front of them.
That is where the recurring description comes from: “They know what I need without my saying it.” This is true in this one area and is the source of many expectations that will later collide with other parts of the relationship. When a person finds someone who meets their deepest need so easily, they unconsciously assume that all their other needs will be met just as easily.
Advice from an Expert Who Does Not Care Much
What meets here: what each person has to perform in public with something the other is good at but dismisses.
This creates a useful kind of guidance: brief, practical, and often phrased as a warning. “Don’t answer that message right now.” “Don’t apologize twice.” “Don’t worry about what will happen a year from now.” These words come from someone who knows the field like an expert but does not consider it important enough to explain, and they land in the area that is most tiring for their partner. This is one of the relationship’s most useful features in daily life: each person helps the other avoid small, repeated missteps in situations where they are trying to perform.
The limit is that the guidance comes without enthusiasm or detail and may sound like a dismissal of what the other person considers important. Someone who has spent days preparing for a job interview will not enjoy hearing “It’s easier than you think” from a person who says it while moving on to something else, even if they are right.
One Skill in Two Different Hands
What meets here: each person’s tool with the other’s quiet skill.
The two share a field: one person presents a method that the other uses quietly in a different way, and neither sees the other’s approach as necessary. A familiar scene follows. One explains the best way to do something; the other listens quietly and then does it their own way. One makes a tidy list of what to buy; the other enters the store and buys what seems right without looking at the list. One sets up a filing system; a week later, their partner is back to the old way because it is “faster.” This is not contempt. Both people are skilled in this field, and neither sees a reason to borrow the other’s method. Over time, each may feel, “They don’t take my approach seriously.”
At the same time, this is one of the relationship’s greatest strengths: each can take over for the other in this field when the partner is away or tired. What another pair might find difficult—one person continuing the other’s work without instructions—is possible here, as long as the person who prefers a particular method lets go of insisting on its details.
The Place Where They Both Stumble
What meets here: each person’s vulnerable point with what excites the other.
What hurts one person is precisely what the other is excited by and wants, even though they are weak at it too. The pair is left without protection across an entire area of life. If the area is feelings and personal relationships, one person longs for emotional honesty that the other cannot offer, while the second longs for openly warm interactions that make the first uncomfortable. If the area is logic and competence, one wants clear organization and the other wants measured results, but neither can provide them. The same pattern appears in a different form around decisiveness and physical comfort, or timing and the ability to read the future.
This has two effects. First, crises in this area are harder for this pair than for many others, because neither person can handle them. Second—and more subtly—one person’s enthusiasm can unintentionally put pressure on the other. They ask for something it hurts their partner to be asked for, and may mistake the partner’s inability to respond for a lack of interest. This is the source of much of the misunderstanding in the relationship.
What They Share and Where They Differ
- ValuesThey belong to neighboring quadras and share some, but not all, values. Their shared values are the deeper ones: each person’s core and deep needs. They therefore agree on what deserves a life’s effort and feel that the other is “from my world.” The different half is more practical and daily: what counts as the right way to handle things, and what deserves enthusiasm in small matters. Most of the friction appears there.
- Interests and rhythmThey stand in neighboring fields of interest and share part of the ground. There is enough common ground for long conversations and enough difference for each to bring something new. They share either decisiveness or flexibility, so their daily life has fewer clashes over schedules: neither rushes the other nor holds them back. This shared timing reduces the effect of other friction.
- Energy orientationOne is extraverted and the other introverted, so social work divides itself naturally. The extravert takes the initiative and opens doors; the introvert protects the inner rhythm and prevents distraction. This arrangement works well and resembles what happens in the closest relationships, helping create a quick sense of familiarity.
How it changes with closeness and time
No relationship stays at one distance or remains the same over time:
By distance
- From a distance
The relationship is quiet, with a light feeling of appreciation. Each sees the other working in a field they also know, notices their competence, and compares their method with their own. This can create early professional respect, or quiet reservation: “They do it well, but that isn’t how it should be done.”
- At a middle distance
Working together reveals both sides. Each can carry a real burden for the other in the shared field, and each also rearranges what the other has done. The first sign of the gap appears too: a task requires something both lack, so it is postponed or handed to someone else.
- Up close
The attraction reaches its height because deep giving works only in close contact: each feels that the other’s presence changes the mood of their days. The gap also becomes impossible to ignore. An illness, a financial crisis, or the need for an honest conversation leaves both without support at the moment they need it most. What protects the relationship is not greater effort but asking less of it. A pair that arranges life so they do not have to handle that kind of task together gets the best of the relationship at the lowest cost. A pair that turns every crisis into a test of love can use up in a month what it built over a year.
Over time
- At the first meeting
It often passes without obvious enthusiasm, though there may be mild curiosity. Each person behaves at first through what they have to perform in public. The other is good at that area but does not value it, so it does not create admiration. One thing does stand out: the other person’s competence in their shared field.
- As they grow closer
Things change when the formality falls away. As each behaves more naturally, their core reaches the other’s deepest need and a strong attraction appears, sometimes surprising both: “I barely noticed them at first, then their presence became what I looked forward to.” At this stage the relationship can seem ideal, and expectations grow high.
- As the relationship settles
The first crisis in the area where both are weak becomes a test that can set the relationship’s direction. They may understand that the limitation is shared and not anyone’s failure, or they may blame each other: “I expected you to understand.” The relationship often settles into a wavering rhythm: deep closeness, then distance after a clash, then a return drawn by the same attraction.
- Over the long term
The relationship can continue despite its gap because what each person gives the other at a deep level is not easy to find elsewhere. The outcome may depend less on the strength of their attraction than on what surrounds them, though this is not the only possible explanation: a pair that builds a network to make up for what they lack can stay together for many years. An isolated pair can wear itself down trying to give each other something neither possesses.
How each sees the other
The same relationship does not look identical from both sides. The clearest difference here is energy orientation: one person lives more in the outside world, while the other lives more in their inner world.
From the Extravert’s Side
The extravert comes to the relationship in motion: taking the initiative, asking for what they need, and measuring things by what can be seen. They find their introverted partner a source of deep reassurance: a steady presence that calms their energy, a view of the world that complements their own, and a quiet ability to do things the extravert explains at length. They often describe them as “the person I feel at ease with, though I don’t know why.”
The extravert’s particular risk is asking this deep bond to provide what it does not contain. They may expect their partner to share their enthusiasm for a subject that matters to them or to take over what hurts them most. They insist and repeat themselves, reading the other’s silence as evasion when it is really an inability. A better approach is to understand where the partner’s ability ends and seek that quality outside the relationship instead of pressing them for it.
From the Introvert’s Side
The introvert comes cautiously: moving forward in measured steps and needing time to believe that the other person’s interest is mutual. They find in their extraverted partner someone who opens the world for them: the courage to take the initiative, energy that gets what has stalled moving again, and a view that gives their days a breadth they had been missing.
The introvert’s particular risk is going silent when asked for something they cannot do. Instead of saying, “I can’t,” they withdraw, and the extravert reads the withdrawal as sudden coldness. A better approach is to name the limitation directly. What seems like rejection of the partner is simply a real limit in a painful area.
Where these accounts meet, we see what makes the relationship confusing to the people in it. Each receives from the other something precious—a sense of ease at the deepest level—and is left without help at the moment when help seems obvious. Someone who does not understand this pattern sees contradictory feelings: “How can they understand me so well and not help with this simple thing?” The answer is that something simple to one person may be beyond the other’s ability.
The relation across areas of life
Friendship
Friendship in Semi-duality is comfortable and enjoyable. The friends have enough similarity to understand one another easily and enough difference for each to bring something new. Each finds someone who listens without judging and gives a brief warning before a small social misstep. The friendship grows slowly, then becomes steady and can survive long interruptions. What joins the friends is not a shared activity that needs refreshing but ease in one another’s presence.
The limit is that it is good company but poor emergency support. When a friend faces a crisis in the field they are both weak in, they find a sympathetic but bewildered person. This can be one of the nicest friendships in ordinary times, while the person needs other sources of help in difficult times. That is not a flaw, but a limit they need to understand.
Romantic Relationships and Marriage
Romance brings out Semi-duality’s strongest feature: a deep and rapid attraction, and a feeling that the other person touches something no one else has. The attraction grows as the distance closes, and both may describe their first months in terms usually heard from people in the closest and calmest relationships. The difference is that calm in those relationships is built on mutual protection; here it rests on attraction alone—a strong foundation at a deep level, with little support in the details.
Shared life brings its test in the same place every time: the field where both are weak. If it is emotions, honest conversations are postponed and what goes unsaid builds up. If it is money and competence, practical matters falter despite their goodwill. If it is decisiveness and health, tasks no one wants to touch accumulate. Successful marriages of this kind recognize the gap and manage it in practical ways: they seek help from someone who can cover it or agree on who will handle it despite the effort. The greatest danger is mistaking a shared inability for a loss of love.
Work and Cooperation
At work, this pair offers a rare advantage: they can cover for each other in their shared field. One can continue the other’s work, take their place when they are away, and understand what they did without a long explanation. This is valuable in teams that need continuity. In a hierarchy, an employee may deeply respect their manager and agree with their general direction, while feeling constrained by interference in execution details. The manager is better off defining the result and its standards, then stepping back from the method.
The limit is that cooperation needs one rule: do not impose one person’s style on the other. If they agree on the result and let each person reach it their own way, the pair works very effectively. If the discussion turns into correcting the method, time is lost and mutual stubbornness grows. The team needs a third person who can cover the field where both are weak; otherwise, an area of work remains neglected, known to everyone but handled by no one.
When they disagree
Every relationship has its own pattern of disagreement. In Semi-duality, conflict tends to pass through three stages:
- The spark
It begins in one of two places. The first is the field where both are weak. A situation calls for honesty, decisiveness, or careful accounting, and each waits for the other to act. The matter is delayed until damage is done, and blame begins. The second is milder but more common: method. One person completes shared work in their usual, visible style; the other quietly redoes it in their own style. The first then feels their effort was not respected.
- Escalation
Conflict grows through disappointment rather than attack. The clash hurts because both know that they understand each other deeply in other areas. It is difficult to believe that the person who understands them without words does not understand them here. The repeated complaint becomes, “I expected you to know.” It gets worse because each person’s enthusiasm falls on the other’s vulnerable point. One asks with good intentions for something that hurts the partner, and the response is sharper than expected.
- A way out
The first and most important step is to name the shared inability: “This is hard for both of us.” That moves the problem from blame to planning and ends much of the resentment that can build here. The next practical step is to decide who will handle the area and agree to leave the method in the shared field to whoever owns the task. The pair often makes peace quickly once they return to what brings them together, because each person’s presence calms the other.
The relation in each pair
The eight pairs share this pattern, but what they exchange differs from one pair to another:
ILE gives their partner a horizon of possibilities that takes them beyond familiar routines. SLI gives ILE calm and a daily rhythm that steadies their scattered attention. They meet in a field they both know: organizing and getting things done—one explains the rule, the other fixes and tests it by hand—and each redoes what the other has done in their own way. They trade brief reminders: SLI reminds ILE to decide and say no; ILE reminds SLI not to weigh themselves down with worry about the future. The area where both stumble is emotions and personal relationships. Their life tends to resemble a quiet workshop: ideas, craftsmanship, and little emotional talk.
SEI gives their partner comfort, reassurance, and attention to the details of the day. IEE brings SEI new people and doors that were not open before. They meet in the field of relationships and atmosphere: one creates warmth in a place, while the other weaves personal connections, and at times they compete over how to handle the same people. They trade brief reminders: IEE reminds SEI to decide and not hesitate; SEI reminds IEE not to worry about what will happen a year from now. The area where both stumble is competence and logical organization: postponed paperwork and neglected accounts. Their life tends to resemble a warm, open home that lacks someone to organize it.
ESE gives their partner warmth, energy, and an atmosphere they lack; LSI gives ESE clear rules and a steady framework to rely on. They meet in handling the concrete world: one prepares comfort and hospitality, the other sets and enforces order. They may clash over whether home is a place for rest or discipline. They trade brief reminders: LSI reminds ESE to calculate whether spending is worthwhile; ESE reminds LSI to leave people room and soften their judgments. The area where both stumble is the future and its possibilities: they fear change and postpone what has uncertain results. Their life tends toward a warm, well-organized home that resists the new.
LII gives their partner clarity and logical order that calm their agitation; EIE gives LII warmth, meaning, and emotional life to fill their silence. They meet in thinking about what is coming: one sees branching possibilities, the other sees a single path things are following. They may disagree over which future is real. They trade brief reminders: EIE reminds LII that people have feelings to consider; LII reminds EIE to count the cost before rushing ahead. The area where both stumble is the body and physical strength: neglected health and avoided confrontations. Their relationship tends toward a major intellectual project whose participants forget to look after themselves.
SLE gives their partner drive, decisiveness, and the ability to take what they want. ILI gives SLE insight into consequences that saves them from rushing. They meet around achievement and rules: one sets and enforces the system, the other calculates what is most efficient and says little. Each may dismiss the other’s method. They trade brief reminders: ILI reminds SLE that possibilities are wider than they seem; SLE reminds ILI to look after themselves and rest. The area where both stumble is personal connection and feelings: quiet closeness and little talk about what is happening inside. Their relationship tends toward a measured alliance: strength and foresight, with coolness in personal matters.
IEI gives their partner a sense of timing and meaning that calms their impulsiveness; SEE gives IEI a push to act and a presence that protects them. They meet in the world of relationships: one colors the atmosphere and moves a group, the other builds loyalties and knows who deserves trust. They may compete to manage the people around them. They trade brief reminders: SEE reminds IEI to care for comfort and health; IEI reminds SEE not to rush after every opportunity. The area where both stumble is accounting and logical organization: money spent without a plan and paperwork that accumulates. Their life tends toward a busy, lively world that lacks someone to keep the books.
LIE gives their partner competence, results, and opportunities that reassure them things are moving. EII gives LIE quiet loyalty and a moral compass they can trust. They meet in reading what is possible: one sees the direction events are taking, the other sees what people could become. They complement one another when they agree and can debate for a long time when they do not. They trade brief reminders: EII reminds LIE that words affect the person hearing them; LIE reminds EII to set a clear standard rather than hesitate. The area where both stumble is the body and decisiveness: mutual exhaustion and postponed confrontations. Their life tends toward conscientious, serious work.
ESI gives their partner certainty in relationships and steady loyalty; LSE gives ESI practical competence and accomplishments that make life easier. They meet in the concrete world: one defends, decides, and protects boundaries; the other masters, organizes, and prepares comfort. They may disagree about when to use force and when quiet work is enough. They trade brief reminders: LSE reminds ESI to simplify and not get lost in scrutiny; ESI reminds LSE that some situations have an emotional side that cannot be ignored. The area where both stumble is the new and uncertain: they turn down opportunities because they are unclear. Their life tends toward a solid, stable home that is slow to let in the new.
What can change its course
The pattern above is what tends to happen when other factors are equal. Four things can shift it:
- SubtypeComplementary subtypes reduce friction in the shared field. A Dominant person leads while a Normalizing person sets things in order, without competing over the same method; the Creative and Harmonizing pairing can work in a similar way. If both have the same subtype, the most visible conflict may be over “how things are done,” because both want control over the field they share.
- Whether the core or the tool is strongerA person with a stronger core has a deeper effect on their partner because their contribution comes from what is not consciously displayed. A person with a stronger tool is more visible and more insistent on their approach in the shared field. A pair with stronger cores tends to feel more attraction and have fewer clashes; a pair with stronger tools works together more actively but argues more over style.
- Maturity and experienceThis relationship depends greatly on whether each person can acknowledge their limits. A mature person knows where their ability ends, says so openly, and asks for help from the right source. Someone who is not yet mature may read their partner’s inability as stubbornness or lack of care, repeat a request in the very area where it cannot be met, and build up disappointment.
- A third person’s presenceThis relationship benefits greatly from a wider circle. Having someone who is good at what both partners lack—a relative, friend, or colleague—can change its entire course: its greatest source of disappointment disappears, while what is most valuable remains. An isolated pair can spend years trying to create for each other something neither possesses.
Strengths and friction
Strengths of the Semi-duality Relationship
- A deep attraction with no obvious causeEach gives the other what they lack at their deepest point simply by being present, creating a real attachment that is hard to explain from the outside. The limit is that the attraction raises expectations in other areas beyond what the relationship can bear.
- A feeling that they know what you needEach reads the other’s deep need without an explanation, giving both a rare comfort in being themselves. The limit is that this understanding covers only one area, though they may assume it applies everywhere.
- Light social guidanceEach helps the other avoid small, repeated mistakes with a brief warning at the right moment, reducing embarrassing situations in daily life. The limit is that the guidance comes without much enthusiasm and can sound like the other person’s concerns are being dismissed.
- An ability to share tasksThey are both skilled in a shared field, so either can carry a real burden or continue the other’s work in their absence. The limit is that this works only if each is allowed to use their own method; otherwise, the exchange becomes an argument over style.
- A similar rhythmThey agree on decision-making and plans, so daily life has less of the scheduling conflict that tires other pairs. The limit is that shared rhythm also means they may both postpone the same task.
Likely Sources of Friction
- A place where they both stumbleThere is a whole area of life where both are weak, leaving neither able to support the other at the moment it is most needed. This eases when they acknowledge the limitation early and seek help from someone who can handle it, rather than waiting for their partner to change.
- Enthusiasm that presses on a sore spotEach asks, with good intentions and enthusiasm, for something that hurts the other to be asked for, and receives a sharper reply than expected. This eases when each learns where the partner’s sensitive point is and asks for what they can give, rather than what the asker wishes they could give.
- Redoing the work “the right way”One person completes a task in their shared field; the other rearranges it their own way, leaving the first feeling their effort was not respected. This eases when they agree on the desired result and leave the method to the person responsible for the task.
- Alternating between closeness and distanceWaves of deep harmony may give way to days of disappointment and withdrawal, without an obvious cause to an outside observer. This eases when they understand that distance follows a clash with the shared gap, not a change in feeling; closeness can return once the situation is handled.
- Silence about an inabilityWhen asked for something they cannot do, one person withdraws instead of saying so, and the other reads that withdrawal as coldness or rejection. This eases when the limit is stated plainly: “This is beyond what I can do; let’s find another solution.”
How to make it work
Good intentions alone are not enough. Small habits can address specific points of friction:
- Name the gap earlyThe pair should identify the area where both stumble—feelings, money and organization, or decisiveness and health—and decide how to handle it: who to ask for help and what to settle in advance. What is named becomes a problem to manage; what stays unnamed becomes a mutual accusation.
- Ask for what is possible, not what is wished forEach person has the right to ask, but it helps to know where the partner’s ability ends, ask them for what they really can do, and seek the rest from the right source. Insisting on a painful point produces only withdrawal.
- Leave the method to whoever owns the taskThis practical rule resolves many daily disagreements: agree on the result, then let each person reach it in their own way without comment. They share a field and both methods can work; insisting on one does not improve the result but harms the atmosphere.
- Read distance for what it isWhen the mood suddenly cools, ask, “Did we run into something neither of us can handle?” before asking, “Have their feelings changed?” Most periods of coldness here come from inability rather than fading affection. Naming the cause can quickly bring warmth back.
- Say out loud what you cannot doA short sentence at the right moment is better than withdrawing: “I can’t do this, but I can do that.” It protects the person being asked to do the impossible and protects their partner from carrying a mistaken interpretation for weeks.
Telling it apart from similar relations
Three relationships are close enough to Semi-duality to be confused with it in everyday life. Each has a question that helps tell them apart:
Duality
It shares the deepest part of Semi-duality: each person’s core nourishes the other’s hidden need, and brief warnings help each avoid mistakes. The other half is completely different: there, the partner’s quiet skill covers each person’s vulnerable point, and their tool excites the other, so both protection and encouragement are present.
Key question: “When a situation touches your weakest area, does your partner quietly take care of it as though it is nothing worth mentioning, or do they stumble there with you?”
Extinguishment
It shares the practical half: both people are good at the same field in different ways and weak in the same area. The difference lies in the deep connection. In Extinguishment, neither person’s core nourishes the other’s need; it lands on something the partner is good at but dismisses, so each person’s enthusiasm becomes something the other warns them about.
Key question: “Does their way of seeing life feed something deep in you, or is it a path you know well and warn them against?”
Mirage
It is the complementary picture. Each person protects the other’s vulnerable point, and each person’s tool excites the other, creating real practical ease. But neither core nourishes the other’s need; the deep attraction is missing, and each person may find the other’s direction unconvincing.
Key question: “Are you captivated by who they are but let down by the practical details, or comfortable with the practical details without being drawn to their direction in life?”
Conclusion
Accounts of Semi-duality agree that it brings strong attraction and deep understanding, is less stable than the two people expect, and stumbles in a particular area where both are weak. It is often described as “close to perfect, but missing one step.” The way the types work helps explain this: attraction comes from each person’s core—what they live without consciously presenting—meeting the other’s deep need, so their contribution arrives as an atmosphere, not an intervention. The gap comes from each person’s vulnerable point being what excites the other, even though that person cannot handle it, leaving the need both uncovered and still being asked for. The struggle over methods comes from one person openly presenting an approach that the other uses quietly in another way. It remains an open possibility—one that would need to be checked by following pairs of this kind over several years and measuring the frequency of closeness and distance—that the relationship is more changeable than others.
The many details in these pages come back to one movement: the two people meet completely at a deep level and differ in the practical layer that protects daily life. From that movement come the attraction that cannot be explained, the understanding that comes before words, a shared inability in one area, and the alternation between closeness and disappointment.
That is where the relationship’s puzzles come from: the person who understands you most may be the least able to rescue you; the deepest thing your partner gives comes effortlessly while the simplest thing you ask of them is impossible; and what you love most about them may be what makes you expect more than they can give. Close in their core, stumbling in their steps, they always return to the same music.
From the outside, this relationship may look like shifting feelings between two people who do not know what they want from one another. From the inside, it is like dancing to the same music, which both hear perfectly: they do not disagree about the melody; only the steps keep going wrong.
What your relationship needs is not for one person to become able to do what they cannot, or for you to pretend the gap does not exist. It is to understand where your shared ability ends and bring someone into your lives who can cover what lies beyond it. The music between you is sound; it is the steps that need to be learned.
This description applies to every pair in a Semi-duality relation.Browse the fourteen relation types