trade union vs labor union

trade union and labor union both are nouns.

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

As nouns, trade union and labor union are synonyms defined as:

trade union and labor union: an organization of employees formed to bargain with the employer

Other synonyms of trade union include brotherhood, trades union, union.

trade union (noun)	labor union (noun)
an organization of employees formed to bargain with the employer	an organization of employees formed to bargain with the employer