Middle Term

In logic, a middle term is a term that appears (as a subject or predicate of a categorical proposition) in both premises but not in the conclusion of a categorical syllogism. The middle term (in bold below) must be distributed in at least one premise but not in the conclusion. The major term and the minor terms, also called the end terms, do appear in the conclusion.

Example:

Major premise: All men are mortal.

Minor premise: Socrates is a man.

Conclusion: Socrates is mortal.

The middle term is bolded above.