Exclusive Or: The logical operator that says either X or Y—but not both—can be true in order for the entire expression to be true.

Fallacy: A proposition's a fallacy if it's always false no matter what.

Inclusive Or: The logical operator that says X or Y—or both—can be true in order for the entire expression to be true.

Instantiation: A specific version, or instance, of an argument.

Logical Connectives: Ideas (and their symbols) that we can use to connect propositions, like and, or, and not.

Logic Gates: A visual representation of connectives that also model what those connectives do.

Predicate: A formal, symbolic logic statement that is the essence of Predicate Logic. Their truth value varies depending on the circumstances.

Predicate Logic: How predicates interact with each other in complex statements.

Proposition: A statement that's either true or false. If you say, "That's a dog over there," we'd know whether it's true or false. Saying something like, "What time is it?" can't really be proven true or false.

Propositional Logic: How propositions work together to make complex statements that are either true or false.

Tautology: A proposition that is always true no matter what.

Truth Table: A table of all possible truth values and truth value combinations for a set of premises.

Universal Gates: Logic gates that can be used to make any other logic gates, as long as you can set them up right.