General agreement between subject and verb?

agreement is a matching relationship between subject and verb

singular subjects go with singular verb phrases

plural subjects go with plural verb phrases.

verbs have singular and plural forms only in the present tense.

This rose looks beautiful (singular), These roses look beautiful (plural)

He likes Rugby (singular) The men like rugby (plural)

past: He liked rugby. The men liked rugby - same verb form

But the be verb has singular and plural forms in both past and present tense.

singular: The box is empty (present) The box was empty (past)

plural: The boxes are empty (present) The boxes were empty (past)