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Number & MeasureGreekEnglish

Dyad

/ˈdaɪæd/noun

A pair treated as a single unit.

The Greek roots

δυάς
dyás
the number two, a pair

Literally: a group of two

Follow a root:δυάς1 word

The story of the word

Pythagorean arithmetic made δυάς a principle rather than a count: the monad was unity, the dyad the first division, the start of difference and therefore of everything measurable. Renaissance mathematicians borrowed the word with that metaphysics still clinging to it. Modern use is flat by comparison, and sociology takes the dyad as the smallest group that can have a relationship at all, the one that dies if either member leaves.

How it travelled
Ancient Greek → Late Latin → English
First recorded
17th century

Same family

dyadicmonadtriadtetrad

In a sentence

Therapists talk about the mother-infant dyad as though it were one organism.

Add a third person and the dyad turns into something with politics.

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