concord
Concord, also termed "agreement", refers to the relationship between two grammatical units that one of them displays a particular feature that accords with a displayed featured in the other. The most important type is the number concord between subject and verb. The subject-verb concord is governed by three complementary principles: the grammatical principle, the notional principle and the principle of proximity. For example, everybody was happy with the decision. Everybody is a singular noun, so the verb is was. In sentence "His family support his idea", the subject "His family" meaning the members of his family, is used as plural notion, so the verb is the plural one "support".
