I often have problems with commas, when to use them and when not.
Several times I got hints, now I'll try to create some example sentences with the hope that they are correct.
1. My father, whose car was stolen a week ago, will buy a new one this week. Correct: the text within the quotes is a non-defining relative clause (you could put it in brackets and the sense of the main clause would not be lost)
2. A woman who doesn't apply make-up hardly exists. Correct: no commas since this is a defining relative clause that functions like an adjective. Put it in brackets and the main clause would read 'A woman hardly exists'! PS: I'd sooner write this as 'There are hardly any women who don't apply make-up.'
3. My computer, which I've had
that has been existedfor 3 years, has become stoo old. As in 1. Note 'which/who' for both non-defining and defining relative clauses but 'that' for defining relative clauses only
4. Computers that
exist forare more than 3 years-old should be replaced by new ones. Correct: defining so no commas. See 3 - you could say 'Computers which ...' - as for which/who v that for defining relative clauses, it's generally a question of preference
5. My cat died, which makes me very sad. Correct: non-defining
6. Tom is a guy who never gives up. Correct: defining
I believe, that:
#1 and #3 need commas because I'm talking about one (a specific one).
#2 and #4 don't need commas because I'm talking about the generality.
#5 could need a comma in order to markedly separate the two parts.
#6 doesn't need a comma but I can't explain it...
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