When the subject is singular, the verb is singular too. Unless it's not. Which is often the case.
Examples:
Singular Subjects: The Plurals of Confusion
Plural Subjects: The Singularities of Chaos
When the subject is modified, the verb is modified too. Unless it's not.
Examples:
Singular Subjects with Modifiers: The Pluralities of Complexity
Plural Subjects with Modifiers: The Singularities of Confusion
Some verbs are irregular, but that's okay. They're like the aunt who still lives in her parents' basement.
Examples: