Who, which, that: does it point or just add?

Lesson 10 · follow-up to Lesson 9 · about 7 minutes · for a miss on Lesson 9 question 7 (commas around a "which" clause)

A who/which clause either points (tells you which one, so no commas) or adds a fact about something already pinned down (so it gets a comma pair). A that clause always points, so it never gets commas.

Your student scored 10/11 on Lesson 9: titles and dash pairs are fixed. The one miss was a which clause: "Mount Everest, which rises nearly nine kilometers, attracts climbers…". It's the same pair idea as Lesson 9, but a clause starting with who or which doesn't look like extra information, so the delete check gets skipped.

The test: cover it. Do you still know exactly who or what?

Purdue OWL's version: "If you leave out the element or put it somewhere else in the sentence, does the essential meaning of the sentence change? If so, the element is essential; if not, it is nonessential" (Commas with Nonessential Elements). For these clauses, the quickest way to answer is to look at the noun in front:

  1. Is it that? No commas, ever. Purdue OWL's rule is to never put a comma before that, and to use who or which for extra information (Defining vs. Non-Defining).
  2. Is the noun already pinned down? A name (Mount Everest, Ms. Ortiz), or a one-of-a-kind thing (my mother, the team's coach). Then the clause only adds: put a comma before who/which and one after the clause. The closing comma sits just before the main verb.
  3. Is the noun general? (students, the bike, people) Then the clause points, telling you which ones. No commas.
Lesson 9 · Q7, worked

✗ Mount Everest which rises nearly nine kilometers, attracts climbers from around the world.

✓ Mount Everest, which rises nearly nine kilometers, attracts climbers from around the world.

There's only one Mount Everest, so it's pinned down and the clause just adds a fact. Cover it: "Mount Everest attracts climbers…" means exactly the same thing. To place the closing comma, find the main verb (attracts) and put the comma right before it.

Points vs adds

✓ Students who finish the test early may read quietly.

✓ My sister, who finished the test early, read quietly.

Cover the clause in the first: "Students may read quietly" means all students, which changes the meaning, so the clause points and takes no commas. Cover it in the second: "My sister read quietly" is still just her, so the clause adds and takes the pair.

The comma can even change the meaning. Purdue OWL's example: "They have two sons who are doctors" suggests there are other sons who aren't, while "They have two sons, who are doctors" means those are the only two (Defining vs. Non-Defining).

What to watch for with your student. When he sees who or which, have him ask out loud: "Do I already know exactly who or what this is?" If yes, he points to the comma before who/which, then to the main verb, and the second comma goes right before it. If the sentence uses that, he can stop: no commas. A useful shortcut: when that starts a clause describing a noun ("the song that we practiced"), a choice with a comma right before it is wrong.

Your turn

The first choice repeats the underlined part as written (the ACT would print "NO CHANGE"), and sometimes it's right. Ask "points or adds?" before answering. The last two questions review Lesson 9.