labor union vs labour

labor union and labour both are nouns.

Word	Noun	Adjective	Verb	Adverb
labor union	Yes	No	No	No
labour	Yes	No	Yes	No

labor union (noun)	labour (noun)
an organization of employees formed to bargain with the employer	productive work (especially physical work done for wages)
	any piece of work that is undertaken or attempted
	a social class comprising those who do manual labor or work for wages
	an organized attempt by workers to improve their status by united action (particularly via labor unions) or the leaders of this movement
	concluding state of pregnancy; from the onset of contractions to the birth of a child

labor union (verb)	labour (verb)
	undergo the efforts of childbirth
	work hard
	strive and make an effort to reach a goal