I'm searching for a word that identifies one of the two "halves" of a dyad. The word "half" seems inappropriate because it suggests a whole that has been sundered. I've also considered "element," "part," "side," "unit," "division," "member," "component," "simple," and "adjunct," but none captures the connotation of something in a reciprocal relationship with its opposite.


2 Answers 2


Monad works for dyads composed of two identical monads. In such cases, a monad is precisely one-half of such a dyad.

From Lexico:

dyad: something that consists of two elements or parts

monad: a single unit


Pollen grains may be released as monads, dyads, tetrads or polyads.’

Twin also works for dyads composed of identical parts.

If the two elements or parts of the dyad are different, you might want to consider the dyad yin and yang, yin being one part of the dyad and yang the other. Wikipedia provides the following for yin and yang:

In Ancient Chinese philosophy, yin and yang (lit. "dark-bright", "negative-positive") is a concept of dualism, describing how seemingly opposite or contrary forces may actually be complementary, interconnected, and interdependent in the natural world, and how they may give rise to each other as they interrelate to one another.

From Lexico:

dualism: The division of something conceptually into two opposed or contrasted aspects, or the state of being so divided.

Yin and yang works for many dyads (almost all?), e.g., male/female, night/day, positive/negative, winter/summer, mother/child, parter1/partner 2, etc., and you could use it in a generalized sense. One of its positive features based on your question: one can't think of yin without thinking of yang and vice versa. They embody an unseverable relationship.

  • Yeah, "yin and yang" is a good idea.
    – Hot Licks
    May 24, 2020 at 0:34
  • @HotLicks Are you pondering an UV? :-) May 24, 2020 at 0:57
  • The word monad is normally used for a self-contained, stand-alone entity. The OP is interested specifically in a word for a component of a dyad, presumably looked at as a component of a dyad, i.e. as something that is not a self-contained, stand-alone entity.
    – jsw29
    May 24, 2020 at 1:16
  • @jsw29 Thanks. That’s why, for the sake of completeness, I broke my answer into two types of dyad, those consisting of identical parts and those consisting of non-identical parts. May 24, 2020 at 1:35

From dyad:

1 : PAIR
specifically, sociology : two individuals (such as husband and wife) maintaining a sociologically significant relationship

As such, a dyad is a partnership, and each of of the people in such a group would be referred to as a partner:

1 b : a person with whom one shares an intimate relationship : one member of a couple
      // Evan and his partner are going on a Caribbean cruise.

So, you could have a sentence like the following:

Jane is part of a dyad. She and her partner are frequently seen together.

If the sense of dyad is not as the above (the question doesn't give specific context, so I assumed the most common meaning), then use one of the following, both from Merriam-Webster.


1 c : one of two mutually completing parts : COUNTERPART
        // She is a kind of complement to me, and we get on famously.
        — Flannery O'Connor


2 a : a thing that fits another perfectly
2 b : something that completes : COMPLEMENT
       // the lead actress and her male counterpart

  • 1
    I think that 'complement' comes very close here. 'Partner' less so, because the word has a very human connotation, and I was thinking of dyad in sense of abstract duality. The trouble with 'complement' as I see it is that, although accurate by definition, the phrase "the complements of the dyad" isn't very clear. I'm not sure why, but it doesn't make me think of the two "halves" as I have called them.
    – clmn
    May 23, 2020 at 19:42

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