coupled vs joined

coupled and joined both are adjectives.

Word	Noun	Adjective	Verb	Adverb
coupled	No	Yes	No	No
joined	No	Yes	No	No

As adjectives, coupled and joined are synonyms defined as:

coupled and joined: connected by a link, as railway cars or trailer trucks

Other synonyms of coupled include linked.

coupled (adjective)	joined (adjective)
connected by a link, as railway cars or trailer trucks	connected by a link, as railway cars or trailer trucks
joined together especially in a pair or pairs	of or relating to two people who are married to each other