8.3 Sentence Structure

When building anything, it is important to be familiar with the tools you are using.  Grammatical elements are the main “tools” you use when when building sentences in longer written works.  Thus, it is critical to have some understanding of grammatical terminology in order to construct effective sentences.

The two essential parts of a sentence are the subject and the predicate (verb portion). The subject refers to the topic being discussed (or the ‘doer’ or ‘agent’ of the sentence), while the verb conveys the action or state of being expressed in the sentence (what the subject does).

All clauses must contain both a subject and a verb. Phrases, on the other hand, lack one or both a subject and a verb, so they need to relate to or modify other parts of the sentence. Main clauses, also called independent clauses, can stand on their own and convey an idea. Dependent clauses, also called subordinate clauses, rely on another part of the sentence for meaning and can’t stand on their own.

Consider the following example in Table 8.3.1:


Table 8.3.1
Sentence 1 is a a simple sentence with one subject (The engineers) and one verb (stood). These are followed by three modifying phrases:
around the tablelooking at the schematics, and for the machine.


Consider the following example in Table 8.3.2:


After they discussed different options, they decided to redesign the components.
Table 8.3.2
Sentence 2 is a complex sentence with one dependent and one independent clause each with its own subject-verb combination (they discussed and they decided). The two clauses are joined by the subordinate conjunction, after, which makes the first clause subordinate to (or dependent upon) the second one.

Being able to identify the critical parts of the sentence will help you design sentences that have a clear and effective subject-verb relationship. Knowing the components will also help you improve your punctuation. If you would like a more detailed review of sentence structure, visit Purdue’s  OWL (Online Writing Lab) Mechanics page.

Sentence Structures

There are four main types of sentence structures: simple, compound, complex, and compound-complex. In the examples above, Sentence 1 is a simple sentence, while Sentence 2 is complex.

SIMPLE SENTENCES have one main clause (one subject + one verb) and any number of phrases. The following are all simple sentences:

      • A simple sentence can be very effective.
      • It makes one direct point.
      • It is good for creating emphasis and clarity.

COMPOUND SENTENCES have two or more main clauses joined by coordinating conjunctions (CC) such as for, and, nor, but, or, yet, so (FANBOYS). You can also connect them using a semi-colon or a colon. By coordinating the ideas, you give them equal weight and importance [Subject + verb, CC  then subject + verb].

The following sentences are all compound:

      • A compound sentence coordinates two ideas, and each idea is given roughly equal weight.
      • The two ideas are closely related, so they should be kept close together.
      • The two clauses may express a parallel idea, and they might also have a parallel structure.
      • Compound sentences need coordinating conjunctions, or they become comma splices, which are a type of run-on.

COMPLEX SENTENCES express complex and usually unequal relationships between ideas. One idea is “subordinated” to the main idea by using a “subordinate conjunction” (like whilebecause, and although); one idea is “dependent” upon the other one for logic and completeness. Complex sentences include one main clause and at least one dependent clause (see Example 2 above). Often, it is stylistically effective to begin your sentence with the dependent clause, and place the main clause at the end for emphasis.

The following sentences are complex; they each follow the same structure: Subordinate conjunction + subject + verb (the dependent clause), subject + verb (the main clause)]:

      • When you make a complex sentence, you subordinate one idea to another.
      • If you place the subordinate clause first, you give added emphasis to the main clause at the end.

*For more information on using emphasis and subordination in your writing, see the chapter Using Emphasis and Subordination.

COMPOUND-COMPLEX SENTENCES have at least two main clauses and at least one dependent clause. Because a compound-complex sentence is usually quite long, you must be careful that it makes sense; it is easy for the reader to get lost in a long sentence. For more information, watch this video on compound-complex sentences from Kahn Academy.

The following sentences are compound-complex:

      • Kate doesn’t like cartoons because they are loud, so she doesn’t watch them. (independent clause, dependent clause, CC,independent clause)
      • After our trip to the beach, school started back, and I was excited to see my friends. (dependent clause, independent clause, CC, independent clause)
      • The dog started barking, so the cat ran away, and since I couldn’t keep up, I decided to stop. (independent clause, CC, independent clause, CC, dependent clause, independent clause)

Additional Resources

"Sentence Structure." Technical Writing Essentials. [License: CC BY-SA]


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Technical Writing at LBCC by Will Fleming is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.