to come into a country of which one is not a native to take up permanent residence
said of a plant or animal: to become established in an area where it was previously unknown
immigration /-ʹgraysh(ə)n/ noun
immigrational /-ʹgraysh(ə)nəl/ adj
[Latin immigratus, past part. of immigrare to go in, from in-2 + migrare to migrate]