Grammar Guide

This guide contains brief descriptions of grammar conventions and their uses within technical writing. To see how these rules apply to punctuation, see BYU-Idaho Online's Punctuation Guide. More guidelines can be found in the Chicago Manual of Style.


A clause is the smallest grammatical unit that expresses a thought. It contains both a subject and verb. Sentences can contain multiple clauses, though clauses are often separated by punctuation and/or conjunctions. For example, I eat is a clause. The sentence, I eat, and Cheryl drinks has two clauses.

Independent vs. Dependent Clauses

Independent clauses can stand alone as a sentence, whereas dependent clauses cannot. The sentence, Although I ate earlier, I’m still hungry, has two clauses, one independent and the other dependent. Dependent clauses generally have a subordinating conjunction or a relative pronoun in addition to their subjects and predicates and do not make sense when used as a full sentence.

Essential vs. Nonessential Clauses

An essential clause restricts the meaning of the term it modifies. The following sentence contains an essential clause (with added emphasis):

All students who do their work should pass easily.

The underlined clause adds vital information to the sentence, so it doesn’t need to be separated with commas.

A nonessential clause adds additional information, but it doesn’t restrict the meaning of the term it modifies. Although removing the clause from the sentence would cost the sentence some meaning, a reader would still understand the meaning of the term. Here’s an example:

Edgar Allen Poe, author of “The Raven,” is a great American poet.

If the underlined portion was deleted, the subject’s meaning wouldn’t change. That makes it a nonessential clause; therefore, it’s surrounded with commas.

Often, essential clauses use the word “that.” For example, “The car that I want is out of my price range.” Nonessential clauses sometimes, though not always, use the word “which.” For example, “My car, which broke down last Friday, won’t be going anywhere anytime soon.”

Essential Clause
Essential to the definition No comma “that"

Punctuation Preffered Usage
Nonessential Clause
Meaningful but not necessary Comma(s) “which"

Conjunctions are words that join clauses together without a colon or semicolon. Three types of conjunctions exist: coordinating, subordinating, and correlative.

Coordinating Conjunctions

Coordinating conjunctions join independent clauses together. Only seven coordinating conjunctions exist: for, and, nor, but, or, yet, so. Commas are generally placed before coordinating conjunctions.

Subordinating Conjunctions

Subordinating conjunctions join dependent clauses to independent clauses. They imply that the dependent clause is less important. Many subordinating conjunctions exist: after, although, as, because, if, once, since, that, though, till, unless, until, when whenever, while, etc. Comma placement depends on how the subordinating conjunctions are used.

Correlative Conjunctions

Correlative conjunctions are pairs of words that connect words, phrases, and clauses. Both parts of the pair have to be used in the sentence to make sense. Examples include either/or, neither/nor, both/and, whether/or, not only/but also.

Sentence Structures

Four sentence structures make an appearance in writing: simple, compound, complex, and compound-complex. Once the difference between each is understood, punctuation mistakes are made far less often.

Simple Sentences

Simple sentences contain one independent clause, which must simply have a subject and predicate. An example is, Bob shouted.

Compound Sentences

Compound sentences consist of two independent clauses combined with either a coordinating conjunction or punctuation like a semicolon. Here are two examples (with emphasis added):

Bob shouted a lot, but he forgave easily.

Bob shouted a lot; he also forgave easily.

See the section about coordinating conjunctions for more details.

Complex Sentences

Complex sentences have one independent clause and at least one dependent clause. Several examples are below, with their dependent clauses underlined:

Although Bob shouted a lot, he forgave easily.

She returned the book after she noticed its damage.

The movie was entertaining, just as I expected.

Experts say that money can’t buy happiness.

Compound-Complex Sentences

Compound-complex sentences have two independent clauses and a dependent clause. An example is provided below, with its dependent clause underlined and the second independent clause bolded:

Experts say that money can't buy happiness; therefore, wealthy people must not be content with their lives.

When punctuating these sentences, it's best to start with the two independent clauses since they are the largest structures. If an editor was punctuating the sentence above, he or she would first place the semicolon, then the comma after therefore. After the independent clauses is examined, the dependent clause is much easier to analyze.

Coming Soon

Phrases (prepositional, noun, infinitive, participial, appositive)

Verb tenses (pg. 142)

Dangling modifiers (pg. 143)

Parts of speech (pg. 136)

Subject and Predicates (pg. 140)


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