Here's why:
* Fugue: A contrapuntal musical form where a single melody (the subject) is introduced by one voice and then imitated by other voices.
* Counterpoint: The art of combining multiple independent melodies simultaneously.
In a fugue, the counterpoint is what provides the melodic accompaniment to the subject as it's introduced and developed by different voices. This counterpoint can be a separate melody, or it can be derived from the subject itself (like an inversion or retrograde).