Late Latin dyad-, dyas, from Greek δυας, from dyo
dyad may refer to:
- dyad (symbol), according to the Pythagoreans, is the principle of "twoness" or "otherness"
- dyad (biology), a pair of sister chromatids occurring in prophase I of meiosis
- dyad (General), consisting of two parts
- dyad (Greek philosophy), Greek philosopher's principle of "twoness" or "otherness"
- dyad (music), a set of two notes or pitches
- dyad (sociology), mostly refers to parents and friends, occasionally to twins
- dyad, in engineering kinematics, a linkage in a planar mechanism that has two possible assembly modes
- dyad, in Obstetrics refers to the pregnant mother and fetus
- dyad (spiritual workshops), is a partner-assisted meditation with rules to prevent trip-laying and abuse
- dyadic tensor, in mathematics
- Dyad, a Canadian band playing traditional American Old Time music