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Essential and non-essential clauses

Essential clauses, nonessential clauses: Both types of clauses provide additional information about a word or phrase in the sentence. Thedifference between them is that the essential clause cannot be eliminated without changing the meaning of the sentence-it so restricts the meaning ofthe word or phrase that its absence would lead to a substantially different interpretation of what the author meant. The nonessential clause can be eliminated without altering the basin meaning of the sentence-it does not restrict the meaning so significantly that its absence would radically alterthe authors thought.

PUNCTUATION: An essential clause must not be set off from the rest of thesentence. A nonessential clause must be set off by commas.

EXAMPLE: Reporters who do not read the stylebook should not criticizetheir editors (if the who...stylebook phrase were deleted, the meaning wouldchange substantially) Reporters, who do not read the stylebook, should notcriticize their editors.

When an essential or nonessential clause refers to a human being oranimal with a name it should be introduced by who or whom. The comma rule still applies. When someone is the subject of a sentence, who should be used.

EXAMPLE: The woman who rented the room left the window open.

When someone is the object of a verb or proposition, whom is used.

EXAMPLE: The woman to whom the room was rented, left the window open.

Whom do you wish to see.

That is the preferred pronoun to introduce clauses that refer to aninanimate object or animal without a name. Which is the only acceptable pronoun to introduce a nonessential clause that refers to an inanimate objector animal without a name? Which may be substituted for that in theintroduction of an essential clause that refers to an inanimate objet oranimal without a name. The use of which should appear only when that is usedas a conjunction to introduce another clause in the same sentence.

EXAMPLE: He said Monday that the part of the army which suffered severe casualties needs reinforcement.

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