Equivocation is a fallacy when a word has more than one meaning and the person arguing confuses the multiple meanings of the word to prove an argument correct. For example, "All trees have bark. All dogs bark. Therefore, all dogs are trees." This is a fallacy because the two times "bark" is used in the argument have very different meanings from each other, while in the argument, the word "bark" should have the same meaning the whole argument. The first meaning of "bark" is the outer layer of a tree, and the second meaning is a shouting sound that a dog makes. The argument does not work because the person changed the meaning of "bark" in the middle of the argument.