immigration vs in-migration

immigration and in-migration both are nouns.

Word	Noun	Adjective	Verb	Adverb
immigration	Yes	No	No	No
in-migration	Yes	No	No	No

As nouns, immigration and in-migration are synonyms defined as:

immigration and in-migration: migration into a place (especially migration to a country of which you are not a native in order to settle there)

immigration (noun)	in-migration (noun)
migration into a place (especially migration to a country of which you are not a native in order to settle there)	migration into a place (especially migration to a country of which you are not a native in order to settle there)
the body of immigrants arriving during a specified interval