A dyad is a group of two people linked in some way. The individuals which form a dyad may be romantic partners, relatives, colleagues, or people who’ve come together because they share similar interests. The individuals in a dyad may be on equal footing or in a hierarchical relationship. In many respects, dyad is simply an alternative word for couple.
Dyad is a Latin word which comes from the Greek word dyas which means the number two or a group of two.