Right - ever since I went to France last month, my iPhone appears to have a bilingual spell-checker on the auto-correct function. Most of the time, when it’s guessing what word I’m spelling, it gives me an English word, but every so often, it slips in a French word.
Does anyone have any ideas what setting I need to tinker with to get it back to just English word suggestions? 
I send texts in English and Spanish. Sometimes I mix them up in one text if the recipient is bilingual. Chose the shorter word, etc.
I thought it would be a problem. But the iPhone seems to adapt. Sometimes, I think it knows which recipients are bilingual.
Interesting, but I’ve not been sending any texts in French, and it’s not just when I’m texting. Some of my texts here on the SDMB get an occasional French word mixed in.
My phone seems to have learned that I sometimes send Spanish texts to my housekeeper and will suggest Spanish words (though not her idiosyncratic dialect spelling) and it also seems to learn proper names from my email.