Definitions of dyad
The word dyad uses 4 letters:addy.
DYAD is playable in:
n. - Two units treated as one; a couple; a pair. 2
n. - An element, atom, or radical having a valence or combining power of two. 2
a. - Having a valence or combining power of two; capable of being substituted for, combined with, or replaced by, two atoms of hydrogen; as, oxygen and calcium are dyad elements. See Valence. 2