In logic, a general categorical statement form the terms of a categorical syllogism. Each general categorical statement consists of four parts, a quantifier ("all" or "some", a subject term, a copula ("are" or "are not"), and a predicate term.

some examples:
All dogs are mammals.
Some men are not nice.

In general each general categorical statement is one of four forms:
A: All S are P.
E: No S are P.*
I: Some S are P.
O: Some S are not P.

*By some quirk of the English language, "All S are not P" is equivalent to "Some S are not P."

Harlan Miller, course notes, Philo 5505 (virginia tech).