brotherhood vs trade union

brotherhood and trade union both are nouns.

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

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

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

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

brotherhood (noun)	trade union (noun)
the feeling that men should treat one another like brothers	an organization of employees formed to bargain with the employer
people engaged in a particular occupation
an organization of employees formed to bargain with the employer
the kinship relation between a male offspring and the siblings