joined vs coupled

joined and coupled both are adjectives.

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

As adjectives, joined and coupled are synonyms defined as:

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

Other synonyms of joined include linked.

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