The term 'highest part' can be described by three different words: ROOF, TOP, and CAP. The word 'ROOF' is a four-letter word that refers to the covering of a building or structure, typically made of tiles or other material, that provides protection from the elements. The word 'TOP' is a three-letter word that refers to the highest point or part of something. Finally, the word 'CAP' is also a three-letter word that refers to a covering or seal for the TOP of a container, or a type of headgear. All three words refer to the highest part of something, and can be used interchangeably in this context.