legation vs foreign mission

legation and foreign mission both are nouns.

Word	Noun	Adjective	Verb	Adverb
legation	Yes	No	No	No
foreign mission	Yes	No	No	No

As nouns, legation and foreign mission are synonyms defined as:

legation and foreign mission: a permanent diplomatic mission headed by a minister

legation (noun)	foreign mission (noun)
the post or office of legate	an organization of missionaries in a foreign land sent to carry on religious work
a permanent diplomatic mission headed by a minister	a permanent diplomatic mission headed by a minister