"Emigrant" vs. "immigrant"
This is about geographical perspective. If you are an American speaking about someone from France who now lives in America, that person is an immigrant (from France). If you are an American speaking about an American who now lives in France, that person is an emigrant (from America).
Now, from the standpoint of the person you describe, it depends on how she sees herself, but the context always has to do with the geographical perspective. She can describe herself as an immigrant to America, or as an emigrant from Sweden. All immigrants are emigrants, and all emigrants are immigrants (that is, unless they remain forever at sea or fail to reach their destination for some other reason). It is the point of reference you wish to stress that should determine the word choice here.
Morton S. Freeman, in A Treasury For Word Lovers, puts it this way:
When a person leaves his country to take up permanent residence in another country, he becomes an emigrant and an immigrant. He is an emigrant upon leaving his homeland and an immigrant upon arriving at his destination.
The term used for a national living abroad, or a permanent resident of foreign origin, is often an "Expatriate" or expat.
A person temporarily or permanently residing in a country and culture other than that of the person's upbringing.
A Useful Mnemonic Device
Not to detract in any way from what Rob has said, let me offer a little mnemonic trick I learned as a kid and which has always served to distinguish the two words:
- An immigrant is an in-migrant, someone who has migrated in to somewhere else. You remember it because in goes with imm-.
- An emigrant is an out-migrant, someone who has migrated out from somewhere else.
The exact reason here is because although in for in works, Latin didn’t use out to mean the opposite of in. It instead used ex, which in compounds like this is represented just by e- alone. More specifically, both words derive directly from Latin, which had paired verbs:
- Latin immigrāre meaning to immigrate in English, originally from im- in + migrāre, to migrate.
- Latin ēmigrāre meaning to emigrate in English, originally from ē- out + migrāre, to migrate.
The same mnemonic device works for the verbs that worked for the nouns
- To immigrate is to migrate in.
- To emigrate is to migrate out.
More /^[ie]?m+igr/i Words
There are a bunch of related terms to each of these. From the OED, we have these three sets:
immigr-: immigrant, immigrate, immigrated, immigration, immigrator, immigratory.
emigr-: emigrant, emigrate, emigrated, emigrating, emigration, emigrational, emigrationist, emigrator, emigratory, émigré.
migrat-: migrate, migrated, migrater, migrating, migration, Migration Age, migrational, migrationism, migrationist, migration myth, migration path, Migration Period, migration-station, Migration style, migrative, migrator, migratorial, migratory, migratory labour, migratory locust, migratory thrush, migratory worker.
Obviously, the migrat- prefixed words are the most abundant, but there are more emi- prefixed words than you may realize.
Qu’est-ce que c’est?
The odd one out in those lists is the one that’s written with diacritics: émigré. Those acute accent marks give away that this a word that took a French holiday while en route to us from Latin. It’s still an emigrant, but a particular kind of emigrant and not just any one one.
Émigré came from the past participle of the verb émigrer in French, which simply meant to emigrate there. Per the OED, an émigré is a noun used either for a Frenchman in specific, or by transference — and I think, now much more commonly — for:
An emigrant of any nationality, esp. a political exile.
Its English pronunciation is /eɪmɪˈgreɪ/.
Wikipedia expands on this definition, giving a bit of context to help tell all these words part:
Émigré is a French term that literally refers to a person who has “migrated out”, but often carries a connotation of political or social self-exile. [. . .] Whereas emigrants have likely chosen to leave one place and become immigrants in a different clime, not usually expecting to return, émigrés see exile as a temporary expedient forced on them by political circumstances. Émigré circles often arouse suspicion as breeding-grounds for plots and counter-revolution.
tl;dr
Just remember that with all these words, imm- means in and em- means out, and you’ll always keep them cleanly separated in your mind.