Because of this, just knowing a dictionary definition may not be enough; you will need to know in what contexts the new word can be used or you could say something that makes no sense. The same applies to colloquial phrases, which many people use incorrectly after hearing them one time (perhaps used by a friend in the wrong context). Understanding the register is very important too, as you don’t want to use slang in a formal context, or alienate people in social situations with overly complex words that only serve to make you look arrogant.