This wasn't a problem in iOS 9 or earlier. However, now iOS 10 has added a new feature such that one doesn't have to switch keyboards to type in another language, which causes trouble: now I have both English and French dictionaries and both keyboards, and for example, when I type "critique" in the English keyboard, a word existing in both dictionaries, iOS will then prompt the French suggestions (de, le, la etc.), even though I never mean to switch to French -- I just want to normally type "critique" as an English word, but of course iOS can't detect my intention.
Anyway, now I want things to go back to what they were in iOS 9 or earlier. And I have to keep both the dictionaries and the keyboards. Is it possible?