But people who are bilingual or trilingual don't suddenly start speaking Spanglish to English-only speakers or mixing three languages into one. You aren't just learning synonyms because otherwise you'd start getting confused about which words are English and which are Spanish, or whatever other language.

Of all the bilingual people I've talked to, they never really say a word from another language in an English sentence randomly or on accident. But many many times they have stopped midsentence because they can't think of the word in English, even though they know it in their native language.