A mathematical abstraction corresponding to an expression of the type βγb; + δ∊ + · · · , in which the elements (dyad symbols) consist of two vector symbols in juxtaposition without the intervention of either the dot (·) or cross (×). Essentially a dyad is an ordered pair of vectors subject to certain rules of operation. The first symbolic factor in a dyad (β in βγb;, for example) is called the antecedent and the second the consequent.