Final answer:
A disjunctive syllogism is a common argument form in logic that states if either X or Y is true and X is false, then Y must be true.
Step-by-step explanation:
A disjunctive syllogism is a common argument form in logic. It states that if either X or Y is true, and X is false, then Y must be true. For example, if the statement 'It is raining or the sun is shining' is true, and it is not raining, then it must be that the sun is shining. This proposition is equivalent to a disjunctive syllogism.