An inference that depends upon ambiguous grammar.

The classic example is posed by the sentence

Woman without her man is lost.

Its meaning and hence what may be properly inferred from it depends upon the placement of the comma.

Is it:

"Woman, without her man is lost," which implies that males need females;

or

"Woman, without her man, is lost," which implies that females need males?

The fallcy of amphiboly takes place if the inference is made without considering the role of the comma.