Protagonist – The leading character or a major character in a drama, movie, novel, or other fictional text
Antagonist – A person who actively opposes or is hostile to someone or something; an adversary
Anticlimax – A disappointing end to an exciting or impressive series of events
Ad lib – This is short for the Latin word ad libitum meaning freely. Essentially, it is the same as improvising lines. Usually used when lines are forgotten
Libretto – The text of an opera or other long vocal work
