Here’s a question a friend just asked re: the following–
I live with my father in the summer, when I’m on vacation from school.
Why does that comma make sense?
The handbook rule (speaking of main and subordinate clauses) is that we use commas when the subordinate clause introduces the main clause, but not when the subordinate clause follows the main clause:
I wake up early because I like to walk the dogs before I go to work.
Because I like to walk the dogs before I go to work, I wake up early.
The “I live with my father” sentence seems to break that rule, but it ‘sounds right,’ so the question is why is that.
Why does the comma after summer sound right?
My guess is that “when I’m on vacation from school” is functioning as a kind of nonrestrictive modifier–a parenthetical–but I’m no linguist … so we will await word from Katharine, who is.
UPDATE: Katharine says it’s nonrestrictive!
It’s a lot of fun having a friend who’s a linguist.
Catherine & Katharine 