An identifier is a NAME or label that is used to identify a particular item or entity. In the context of a crossword puzzle, an identifier can be a four-letter word or a five-letter word. The four-letter word, NAME, is often used to refer to a person, place, or thing. The five-letter word, NAMER, is usually used to refer to someone who names or identifies something. Both words are commonly used in crosswords and other puzzles as identifiers.