François CholletVerified account

One of the most difficult things to master in a foreign language: cases where the target language uses multiple words (subcategories) for a concept for which your previous languages only have one word. You're simply not used to parse reality into these new subcategories.

A simple example would be counters in Japanese. In European languages, a counter is just a number, so you would say, "three birds, three peanuts, three sheets of paper, three pens, three cars". In Japanese, a counter conveys not just quantity but also various object properties