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It's All Relative
2007, Q1 (July 12, 2007)
By Andrea Wenger, Carolina Chapter Senior Member

Sometimes grammar is easier when we don’t think about it. We learn to speak long before we learn to write; we develop a natural understanding of language without knowing the rules. While a three-year-old will say, “one foot, two feet,” a five-year-old might say, “one feet, two feets.” A little knowledge is a dangerous thing.

When it comes to relative pronouns, incomplete knowledge may lead to frustration and confusion. The pronouns that, which, who, and what serve as relative pronouns when they introduce a relative (or subordinate) clause. The Chicago Manual of Style and other resources specify clear guidelines for relative pronoun usage, which depends primarily on two things:
  • Is the clause restrictive or nonrestrictive?
  • Is the pronoun’s antecedent human or non-human?

A restrictive clause limits or defines the noun it modifies in some way; it’s integral to the meaning of the sentence. It’s not set off from the main clause using punctuation.

The shoes that I bought last week fit perfectly, but the shoes that I bought yesterday are too tight.

A nonrestrictive clause provides supplementary information and is properly offset by a comma (or a pair of them, if the clause doesn’t begin or end the sentence). You can also use em dashes to offset a relative clause. But don’t mix a comma with a dash around a single clause.

The concert, which Diane enjoyed immensely, included eighteenth-century Irish folk music.
Because of traffic — which was unusually heavy, due to construction — Rafael almost missed his flight.


Use “that” as the restrictive relative pronoun when the antecedent is non-human. “That” can also be used when the antecedent is human, although “who” is generally preferred.

The bird that I saw through my binoculars was red and black.

Avoid using “that that.” If the word “that” precedes the relative pronoun, use either “that which” or “what.”

I trust that which I see with my own eyes.
I trust what I see with my own eyes.

“That” can also function as a subordinating conjunction when introducing a dependent clause. In this case, it doesn’t have an antecedent:

She knew that he would call.

It’s acceptable to drop “that” if the meaning of the sentence is clear without it. This is a good practice particularly when another “that” appears in the sentence:

She knew he would call that afternoon.

In the above example, using “that” after “knew” is unnecessary. “He” can’t be the object of “knew” (because “he” is the subjective case), so “he” must be the subject of a dependent clause.

But omitting “that” presents a miscue to readers when (a) the verb can be transitive or intransitive, and (b) the noun that follows can serve as either a subject or an object:

Ensure the integrity of the seal is not compromised.

In the above example, readers may suffer momentary confusion because “integrity” first appears to be the object of “ensure,” when in fact it’s the subject of “is.”


Use “which” as the nonrestrictive relative pronoun when the antecedent is non-human. Don’t use “which” if the antecedent is human, unless the antecedent is a mass noun.

My cat Pumpkin, which I got on Halloween, is orange and white.
The San Diego team, which won its last game, will go to the playoffs.

As mentioned above, you can also use “which” as the restrictive relative pronoun following “that” to avoid saying “that that.”

Who and Whom

“Who” is the only relative pronoun that declines — that is, it uses a different form (whom) in the objective case. Use “who” or “whom” as the restrictive or nonrestrictive relative pronoun when referring to humans.

My brother who visited last May just got married. (restrictive — I have more than one brother.)
My brother, who visited last May, just got married. (nonrestrictive — I have only one brother.)
My brother, whom I visited last May, just got married. (nonrestrictive, objective case.)

Note that indulgent grammarians permit using “who” and “whom” when referring to pets:

My cat Pumpkin, whom I got on Halloween, is orange and white.

Still having trouble figuring out when to use “who” and “whom”? Remember that “who” functions like “she,” while “whom” functions like “her”:
  • “Who” serves as the subject of a verb or as the complement of a linking verb.
  • “Whom” functions as the object of a verb or a preposition.

In two situations, however, it gets tricky:

1. Always use the objective case (whom) as the subject of an infinitive. If the choice were between “he” and “him,” you’d probably get this right without thinking about it:

I know him to be an excellent guitar player.
You know whom to be an excellent guitar player?

2. If a dependent clause is the object of a verb or a preposition, but the relative pronoun is the subject of the dependent clause, use the subjective case (who) for the relative pronoun:

I saw who took the last piece of pie.

But knowing when it’s correct to use “whom” is only part of the challenge. “Whom” has nearly disappeared from spoken language, so its use in written material can sound jarring or pretentious. And if the reader is focusing on your language, he’s not focusing on his task. Your primary goal is effective communication, not grammatical correctness.

My cat Pumpkin, who I got on Halloween, is orange and white.

Sounds better, doesn’t it?

So the choice depends in part on your audience and purpose. In general, don’t use “whom” if it’s likely to sound unnatural, and don’t use “who” if it’s likely to sound incorrect. In user manuals and other instructions, the tone should be authoritative but not stiff. In journal articles or annual reports, a more formal tone may be appropriate. Follow your style guide.


“What” refers only to inanimate objects or abstractions. Unlike other relative pronouns, “what” takes no antecedent. Why? Because “what” replaces “that which,” where the indefinite pronoun “that” is the antecedent of “which.”

Diane could only imagine what had spooked the horse.
Rafael told no one what he had seen that night.


“Whose” is the possessive of “who,” “which,” and “that” — so you can properly apply it to humans or non-humans:

Give the prize to the respondent whose application arrives first.
There’s the dog whose owners live in the pink house.
Energy efficiency is an idea whose time has come.

Compound Relative Pronouns

These include whoever, whomever, whatever, and whichever. They follow the same rules as their simple counterparts.

Whosoever and whatsoever are acceptable; but whosoever sounds arcane, while whatsoever is needlessly verbose.

Remote Relatives

Remote relatives are relative pronouns separated from their antecedents, and they may seem to modify an intervening noun.

The birdfeeder on the deck, which I filled with sunflower seeds yesterday, was empty this morning. (Presumably, it was the birdfeeder, not the deck, that was filled with sunflower seeds.)

For the sake of clarity, place the relative pronoun immediately after the noun it modifies. Or, if the sentence is long and unwieldy, make two sentences.

I filled the birdfeeder on the deck with sunflower seeds yesterday. But this morning, the feeder was empty.

Don’t be afraid to repeat the noun and eliminate the relative pronoun. In creative writing, readers may find repetition boring — but people don’t read technical writing for entertainment.

Relative pronouns are versatile words; sometimes, they’re too versatile. Grammatically, it’s correct to say, “I know that that that that man told me is a lie.” Stylistically, it’s a nightmare. “I know that what that man told me is a lie” is better. But “That man lied to me!” is better still. Sometimes the best usage of a relative pronoun is to eliminate it altogether.

As technical writers, our job is to make complicated material simple. Relative pronouns, by definition, introduce complexity into a sentence.

Avoid using a complex sentence (that is, a sentence containing a dependent clause) when a compound sentence — or better yet, a simple sentence — will serve. Like compound sentences, complex sentences incorporate two ideas. But complex sentences also make one idea subordinate to the other. So the reader must grasp not only the ideas, but the relationship between them — all within the space of a single sentence. When used well, complex sentences make our writing more interesting and varied. When used poorly, they make it more difficult to understand.

The key is to be concise. In Sin and Syntax, Constance Hale cites the following quotation from Mark Twain—a sentence comprising two independent clauses and two dependent clauses, but only nine words:

“When angry, count to four; when very angry, swear.”

Nothing complicated about that.

Andrea can be reached at andrea dot wenger at us dot schneider-electric dot com End of article.

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