What's the opposite of smile. Is it frown or scowl. Or, ther're the same. Are they really the same when it comes to their usage? Like, could I always use frown instead of scowl. If not, please give some examples. Which of these is for a mad look and for a sad look.
Of course, in many cases these overlap - something you dislike may anger you. To get used to which word to use in which context, you need to read novels and newspapers, rather than dictionaries and grammar books.
A couple of examples
He frowned at the interruption. He was reading the last paragraph of the letter, and wanted to finish it before dealing with anything else.
He scowled at his opponent; he was ready for a fight.