equivocation

Using a word in a different way than the author used it in the original premise, or changing definitions halfway through a discussion. When we use the same word or phrase in different senses within one line of argument, we commit the fallacy of equivocation. Consider this example: "Plato says the end of a thing is its perfection; I say that death is the end of life; hence, death is the perfection of life." Here the word end means "goal" in Plato's usage, but it means "last event" or "termination" in the author's second usage. Clearly, the speaker is twisting Plato's meaning of the word to draw a very different conclusion. Compare with amphiboly, below.