When you learn a foreign language, one of the things that causes problems are false cognates, which are words that sound similar but can have quite different meanings. The classic example for Spanish students is ‘embarazada’ which sounds like the English word ‘embarrassed’ but actually means ‘pregnant.’ If an American woman tries to say that she is embarrassed using ‘embarazada,’ the reaction of her cohorts will teach her her error promptly. She won't make that mistake a second time.

It's a little trickier when the meanings of the false cognates are much closer in the two languages. In that case there is much more likely to be continuing confusion and cross-cultural mis­com­munication, and that miscommunication can be both on the dictionary-meaning level and on the emotional level. A case in point are the words туалет and toilet. In American English toilet means the actual device one sits upon, and in Russian туалет means the room in which the toilet (but usually not the bathtub) is located. Since the Russian word is so similar to the English word, American students of Russian only have to hear it once to remember it forever, and they promptly start producing sentences like:

In terms of grammatical communication it is a perfectly adequate sentence, but the student hasn't said quite what he thinks he has said, and there is a very good chance he has just committed a cultural faux pas. The sentence is a little too direct for polite company, and simply saying you want to go to the toilet summons up unpleasant images of... well, you get the idea. In American English we avoid those images because the word “bathroom” focuses on the ‘bath’ idea; that is, there is a subtle association with cleanliness, not urination or defecation. So to avoid being quite so direct, the Russians have several ways of euphemistically expressing the idea. The one I use most is «помыть руки», which word-for-word means “to wash the hands”:

If you say it that way, there will be a bit of ambiguity to the Russian, who won't necessarily be sure if you need the toilet or the sink, but since in a Russian apartment the room with the toilet is usually right next to the room with the bathtub and sink, they will lead you right to where you need to go for either purpose. Of course, if you are not directly discussing bodily functions, it's perfectly fine to use the word туалет:

The social contexts that affect the direct use of the word туалет are complex. My friend Tanya assures me that if she is at a restaurant with a mixed group of men and women, she never uses the word туалет. Instead she would just stand up, say «Я сейчас приду» “I’ll be right back,” and then leave. But if she is with just her female friends at the restaurant, she might well say «Я пойду в туалет» “I'm going to the bathroom,” and since she is with her friends she might add to one of them «Ты хочешь со мной?» “Do you want to come with me?” Similarly a Russian man in mixed company will use euphemistic phrases like the ones mentioned before or «Я отойду на минутку» “I'll step away for a moment.” (But unlike Russian women, a Russian man won't ask a buddy to go to the bathroom with him.)