structure of the sentence.

Fallacy of four terms

Equivocation in a syllogism (a chain of reasoning) produces a fallacy of four terms quaternio terminorum. Below is an example:

: Since only man [human] is rational.
: And no woman is a man [male].
: Therefore, no woman is rational.

The first instance of "man" implies the entire human species, while the second implies just those who are male.

Motte-and-bailey fallacy