(1):

(n.) A connective or connecting word; an indeclinable word which serves to join together sentences, clauses of a sentence, or words; as, and, but, if.

(2):

(n.) The act of conjoining, or the state of being conjoined, united, or associated; union; association; league.

(3):

(n.) The meeting of two or more stars or planets in the same degree of the zodiac; as, the conjunction of the moon with the sun, or of Jupiter and Saturn. See the Note under Aspect, n., 6.