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Write Clearly: Grammar

Note about this Guide

In this guide, bold font and parentheses are used to draw attention to subjects, verbs, conjunctions, conjunctive adverbs, commas, colons, semi-colons, and periods. Screen Reader Users: Please set your program’s punctuation level to 'most' or 'all' in order to hear the content in parentheses.

Dependent Clauses

A complex sentence contains one independent clause and one or more dependent clauses. Dependent clauses can function in the sentence as nouns, adjectives, or adverbs

Noun Clauses

Noun clauses function as nouns in the sentence and can be used as subjects, objects, predicate nominatives, and objects of prepositions.

What is most important to him is his family.
(What is most important to him is the noun clause acting as the subject)

The critic writes that Al Purdy is the best poet in Canada.
(That Al Purdy is the best poet in Canada is the noun clause acting as the object)

You are what you eat.
(What you eat is the noun clause acting as the predicate nominative)

She is very suspicious about what he said.
(What he said is the noun clause acting as the object of the preposition about)

Adjective Clauses

Adjective clauses start with a relative pronoun such as who, which, or that and function as adjectives. The pronoun refers to a noun that usually precedes it directly.

The woman who bought the red dress is my aunt.
(Who bought the red dress is the adjective clause modifying the noun woman)

That dress, which is my favourite, was expensive.
(Which is my favourite is the adjective clause modifying the noun dress)

The problem that he solved was a difficult one.
(That he solved is the adjective clause modifying the noun problem)

NOTE: Use commas around an adjective clause to indicate that the information in it is not essential to the sentence, i.e., not needed to identify the noun. Absence of commas, on the other hand, indicates the information is essential to the sentence.

The bull that is in the pasture belongs to Joe.
(That is in the pasture with no commas is an essential adjective clause modifying bull; as an essential clause, it suggests that, of all the other bulls on the farm, the one in the pasture is being identified as belonging to Joe)


The bull, which is in the pasture, belongs to Joe.
((comma) which is in the pasture (comma) is a non-essential adjective clause modifying bull; as a non-essential clause, it suggests that there is only one bull on the farm, so the writer is giving non-essential information by mentioning that it is in the pasture)

NOTE: The word that is used to introduce an essential clause (without commas), whereas which is used to introduce a non-essential clause (with commas). Some grammar textbooks suggest which can be used for either essential or non-essential clauses, whereas others recommend using which only for non-essential clauses.

NOTE: A pronoun (such as which, that) must always refer specifically to one noun. The word which is often used incorrectly to refer to the idea represented by the whole sentence.


Incorrect: Your essays should be submitted on time, which is one way to be a successful student.
(Vague reference because the pronoun which in this sentence refers to neither time nor essays.)

Correct: One way for you to be successful as a student is to submit your essays on time

Adverb Clauses

Adverb clauses function as adverbs in the sentence, modifying verbs, adjectives, or adverbs. They may tell how, why, when, where, etc. Conjunctions used include although, after, if, because, while, when, since, whether, etc.

When I arrived at the University, classes had already started.
(When I arrived at the University is the adverb clause modifying the verb started)

Stan is happy because he received a good grade on his history midterm.
(Because he received a good grade on his history midterm is the adverb clause modifying the adjective happy)

Although Bob is intelligent, he doesn’t work very hard.
(Although Bob is intelligent is the adverb clause modifying the adverb hard)

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