Delegate, deputy, representative designate a person who stands in place of another or others. It is not always possible to distinguish these words, for they are all used in different places or at different times to designate persons whose offices and functions are much the same.
Nevertheless there are broad or general differences in meaning which may be observed, although they will not always afford a clue as to why this person or that is called a delegate, a deputy, or a representative.
Delegate applies to a person who is sent or is thought of as being sent with a commission to transact business for another or for others; it often specifically designates a person who is sent by an organized or unorganized body (as a branch of a larger organization or a group of employees) to a meeting where questions pertaining to the welfare of the entire organization or industry will be discussed and voted upon.
Delegate usually implies powers that are not plenary but are somewhat modified (as by the delegate’s own power to influence or convince others and by the need of his bowing to the will of the majority).
Deputy applies to a person who is given authority to act for another or for others as a substitute or as an agent; it is particularly applicable to a person who has been chosen to perform a part or the whole of an official’s duties.
Representative applies fundamentally to a person who takes the place of one or more persons in a situation where for some reason the latter cannot be. It may be used of a person engaged to do or to transact business for another or others.
However it is more often employed in reference to one who takes the place of a larger group (as the electorate of a particular region) and thereby belongs to a body of men who as a whole are charged with making the laws for the state or nation.
The terms are often used to imply the same or very similar functions in different places; thus, approximately the same body is called the House of Representatives in the United States and the Chamber of Deputies in the Republic of France; there is little difference except in voting powers between a representative from a state in the United States Congress and a delegate from a territory.