Frequency: The word is one of the 700 most common words in English.
1.
You say of course to suggest that something is normal, obvious, or well-known, and should therefore not surprise the person you are talking to. (SPOKEN)
Of course there were lots of other interesting things at the exhibition...
'I have read about you in the newspapers of course,' Charlie said...
The only honest answer is, of course, yes.
= naturally
ADV: ADV with cl
2.
You use of course as a polite way of giving permission. (SPOKEN)
'Can I just say something about the cup game on Saturday?'-'Yes of course you can.'...
'Could I see these documents?'-'Of course.'
CONVENTION [formulae]
3.
You use of course in order to emphasize a statement that you are making, especially when you are agreeing or disagreeing with someone. (SPOKEN)
'I expect you're right.'-'Of course I'm right.'...
'You will strictly observe your diet: no wine or spirits, very little meat.'-'Of course.'
ADV: ADV with cl, ADV as reply [emphasis]
4.
Of course not is an emphatic way of saying no. (SPOKEN)
'You're not really seriously considering this thing, are you?'-'No, of course not.'
CONVENTION [emphasis]