Again, the key word is PARENTHETICAL (that is, unessential to the structure of the sentence):
Alex (, the chess champion,) never seems to study.
That chess champion (, the one who never seems to study,) is named Alex.
Alex (, whom everyone likes,) loves everybody.
Alex (, who hates to sit in his room,) also hates to work out.
But note:(As a matter of fact,) Alex (, the rugby team captain,) (, who never appears to work hard,) is (, believe it or not,) the smartest (, if not the handsomest,) student ever to come out of Bloomsburg University (, without exception).
A tennis player who hates to work out is not necessarily a loser.
Again, "a tennis player who hates to work out" is all the subject of the sentence.
"who hates to work out" is a dependent clause, but it does not require any commas because it is not parenthetical; it cannot be left out. It is not true that "a tennis player is not necessarily a loser"; it is true that only "a tennis player who hates to work out" is.
Courses that don't take much work will not necessarily get you into grad school.
Here we come to the that/which issue. Use "that" when the clause ("that don't take much work") is necessary to the sentence (and so needs no commas). Use "which" if the clause is parenthetical, as in:
Gym courses, which don't take much work, will not get you into grad school.
The basic sentence here reads
Alex is the smartest student ever to come out of Aristotle University.
The rest is all parenthetical. In fact much of what we
all write (and say) is parenthetical.
If you can find the main verb of a sentence, you will be able to identify the rest of the structure--and therefore be able to punctuate it correctly.
Return to Punctuation page