Hey,

Knowing the meaning of a word, or at least thinking that you understand how and when to use a word does dictate your understanding and how you use it. Before we can talk or build our vocabulary all we do is hear words, learn its meaning and try to identify its context so that we can use it too. But after that, we can manipulate a word and use it independantly of its meaning because of a new understanding of its use, say for slang, cliches and colloquial terms.