GENERAL: Two elements a and b agree if they have at least one feature in common. Two elements a and b are in an agreement relation if they must agree in some way. A traditional term for agreement is concord. EXAMPLE: the subject and the finite verb in (i) are in an agreement relation: they must have the same features for person and number.
(i) John[3p,s] is[3p,s] reading
SYNTAX: Recently, it has been proposed that agreement is the relation between a specific head AGR and its specifier (= specifier-head agreement). Subject-verb agreement is then reduced to agreement between AGR, which is a functional projection of the agreeing verb, and the element (the subject) in the specifier position of the AGRP. Likewise, assignment of structural Case is reduced to