The crossword solution for the term 'WHAT IS 'JUST A NUMBER'?' is AGE, which is a three-letter word. AGE is a concept that is used to measure the length of time that a person or thing has existed. It is often used to describe how old someone is, but it can also be used to refer to the amount of experience or knowledge someone has. AGE is often seen as just a number, meaning that it does not necessarily determine one's worth or ability.