Quaternio terminorum

Four-term fallacy or error

Quaternio terminorum is a form of fallacious syllogism, which instead of having three terms like any valid categorical syllogism, actually has four given the double meaning of one of the terms.

Example:

Men are essentially free, and women are not men;

therefore, women are not free.

“Men” (human beings) in the major premise does not have the same meaning as “men” (male) in the smaller premise, so there are 4 terms and not 3.-