- You use because of to show the reason for something.
- There's no class because of the holiday.
- We couldn't leave the island because of the bad weather.
- Because is followed by a clause (e.g., because it was good), while because of is followed by a noun phrase (e.g., because of the weather).
- Watch out for ambiguity after a negative first clause, as in "The case was not brought before the committee because of the incident the night before". This can be read either as a reason (the incident happened and so the case was not brought), or a denial of a reason (the incident happened, but this is not why the case was brought).