of course - Definition from Longman English Dictionary Online

of course
adverb

of course S1 W1

1 used to show that other people probably already know what you are saying is true, or expect to hear it:

Look up a word starting with D or S for samples of headword or sentence pronunciations on the LDOCE CD-ROM

Well, she won, of course.

You should of course keep copies of all your correspondence.

Of course there will be some difficult times ahead.

2 spoken also course informal used to emphasize that you are saying 'yes' when someone asks your permission to do something:

'Can I ring you back in a minute?' 'Yes, of course.'

'Is it OK if I have another cup of coffee?' 'Course, help yourself.'

3 spoken also course informal used to emphasize that what you are saying to someone is true or correct:

'Do you really believe her?' 'Of course I do!'

'I hope this idea of yours works.' 'Course it'll work.'

4 spoken used to show that you accept or agree with what someone has just said:

'Don't get angry. She's only thirteen.' 'Of course.'

'The correct answer is 83.' 'Oh, yes, of course.'

of course not/course not

spoken used to emphasize that you are saying 'no' to something:

'Have you been reading my e-mail?' 'Of course not!'

'Do you mind if I bring a friend?' 'No, of course not.'

POLITENESS

Use of course as a polite and friendly way of agreeing to something • 'Can I borrow your pen?'- 'Of course'. • Of course I'll help you. • 'Do you mind if I smoke?' - 'Of course not'. Do not use of course as a reply when someone asks you for information, because this can sound rude and unfriendly. If, for example, you asked someone • 'Is this the Swallow Hotel?' and they said • 'Of course it is' it would sound as though they thought the answer was obvious and that you were stupid to ask them.

Definition from the Longman Dictionary of Contemporary English
Advanced Learner's Dictionary.

Dictionary pictures of the day

Do you know what each of these is called?