There are three concords in simple sentences:
1. A finite verb agrees with its subject in number and person ( cross949).
2. A word in apposition with another word agrees with it in case ( cross976).
3. An adjective agrees with its substantive in gender, number, and case ( cross1020).
(For the concord of relative pronouns, see cross2501.)
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].