Proposition: Declarative sentence that is true or false (not both). Propositional variable: Variable that represents a proposition. Compound proposition: New proposition formed from existing propositions (potentially) using logical operators. Note: A propositional variable is one example of a compound proposition. Truth table: Table with one row for each of the possible combinations of truth values of the input and an additional column that shows the truth value of the result of the operation corresponding to a particular row.