a person who assists or gives aid and support; helper.
2.
a person who is subordinate to another in rank, function, etc.; one holding a secondary rank in an office or post:
He was assistant to the office manager.
3.
something that aids and supplements another.
4.
a faculty member of a college or university who ranks below an instructor and whose responsibilities usually include grading papers, supervising laboratories, and assisting in teaching.
mid-15c., assistent "one who helps or aids another," from Middle French assistent, adjective and noun, properly present participle of assister (see assist (v.)).
adj.
mid-15c., "helpful, of assistance," from Middle French assistent (see assistant (n.)).