(1):

(n.) A reference to decided cases, or books of authority, to prove a point in law.

(2):

(n.) An official summons or notice given to a person to appear; the paper containing such summons or notice.

(3):

(n.) The act of citing a passage from a book, or from another person, in his own words; also, the passage or words quoted; quotation.

(4):

(n.) Enumeration; mention; as, a citation of facts.