Adjutant is a noun that refers to an assistant.

The Latin word adjuvare (ad joo VARE ay) means ‘to assist.’ Our word of the day has evolved from this word, first in reference to a military officer acting as an assistant to a senior officer. Later the word came to refer to any kind of an assistant. For example:

When I first took the job of manager’s adjutant, I assumed I’d be in charge of the department. But I later learned that I was simply the assistant to the actual manager.