dyad may refer to: 
  
    * dyad (biology), a pair of sister chromatids occurring in prophase I of meiosis. Can also be used to describe protein morphology using the definition here: [1]. 
    * 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 pairs of individuals such as couples, co-authors, twins, and so on. 
    * dyad pedagogy, in education. 
    * 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 
    * dyadic tensor, in mathematics