Agonist & Antagonist?

what is the difference between them? In biology "agonist" is used for a substance which combine with an organ's receptor and activate its action. It is also used for a muscle.
The permanent status "antagonist" refers to a substance which will block the receptor. It is also used to the opposing muscle (when one muscle contracts, the other relaxes).
An agonist is simply someone in an argument or conflict. doesn't business WHO.
An Antagonist is any character within a book/story/poem that works AGAINST the main personality (also called the protagonist)
Well they both are greek words.
An AGONIST is someone who struggles by himself.
An ANTAGONIST is the other one who does duplicate thing as you. (especially within work)
Oops, i was too hectic to answer and did not see the MEDICINE. Sorry!
if ur refereing to literature afterwards the guys who answered first wld b ur ans however if abt anatomy or medicine later they r simply the relationshi[ between muscles where the endeavour of one opposes the other. typical eg is the biceps and the triceps. when the biceps r flexed the triceps r relaxed and vice versa.