Díada is the dynamic of small social groups, referring to social groups that are formed by two persons. Marriage, friendship or amorous relationships are groups of this type.
In groups formed of two the social interaction is a lot more intense than in larger groups. In a relationship between two, clearly there is no third person that wants competes for the others attention. Due to that, in those specific groups, the strongest and most meaningful connections are created.
On the other hand, those groups are a lot more unstable and temporary as they depend on the effort of both members. In exchange, more numerous groups, the desertion of a member has not such strong influence on the survival of the group.
This is why today, we meet a group of two in which the effort, processes and achievements were kept alive.