Q: Why can’t a nose be 12 inches long?
A: If it was, then it would be a foot!
Explanation: In the standard system of measurement, the system that is used in the United States, 12 inches equals one foot (about 30 cm). A foot is also a body part, just as a nose is a body part. This joke plays on the double meaning of the word “foot.” And of course, a nose cannot be a foot!