Who, Whom, Which, and That
by Cherie Tucker
There are two
rules concerning these words when they are used to introduce
descriptive information in a sentence. First, who and
whom refer to people; which and that refer to
He is the man who sold us the bridge.
We have your signature, which closes the deal.
These are the times that try men’s souls.
Second, some constructions using these words require a comma, but
some do not. The comma alters the meaning, so you must decide what
it is you wish to say. If the information introduced by who/m
is essential to the meaning of the sentence, there should be NO
comma. Test by leaving that part out.
He only dates women who can
He only dates women.
Since the who clause determines the description of “women” in
the sentence, there should be no comma. By contrast, if the clause
is merely informational, it must be set off by commas.
The women, who had been standing vigil since
noon, finally went home.
In this sentence, the fact that the women were standing vigil is not
essential to the message that they went home. The commas are
necessary, acting like parentheses.
With that and which, the comma use is easier to
determine. Generally, that introduces essential information,
and which introduces non-essential.
book that changed her life had been banned.
The book, which they later banned, changed her life.
In the first example, that restricts the meaning of “book” to
only one book, the life-changing one. In the second example, the
fact the book was banned is incidental to the change in her life and
must be set off by commas.
There are times when you can leave these little words out, but only
if the omission doesn’t lead to misreading. In the sentence, “We
knew that Bill was guilty,” it seems logical that you could
leave that out. However, if the first part appears at a page
turn, you have “We knew Bill,” which isn’t what you are saying. If
your sentence reads, “We knew that he was guilty,”
then leave that out. Since no one over the age of three
says “We knew he,” that omission is a safe one.
Cherie Tucker, owner of GrammarWorks, has taught writing basics to
professionals since 1987, presenting at the PNWA conference.
She currently teaches Practical Grammar for Editors at the
University of Washington’s Editing Certification program and edits