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Understanding Grammatical Structures of Sentences

Sentences are the building blocks of thought. Without sentences and the context in which they appear, communication would be impossible. — Stephen R. Covey

Sentences are usually defined as the building blocks of thoughts—written or unwritten messages—because each sentence is a unit of meaning, a complete thought.

Sentences are fundamental to language, yet they are hard to define. Webster’s New Collegiate Dictionary, says that a sentence is a “grammatically self-contained speech unit.”

Many teachers would call it “a complete thought” and perhaps add that it usually contains, at a minimum, subjectOpens in new window and a verbOpens in new window.

Problem is, that definition would seem to rule out the following, all of which are sentences:


All written sentences begin with a capital letter and end with a mark of punctuation, usually a period but sometimes a question mark or an exclamation mark.

This convention applies to all sentences; even those with only one word and those in which words that are understood have been left out.

Most sentences are longer than one word and do include both the subject and the verb:
  • The invoice was late.
  • Because the invoice was late, we could not include it in accounts payable for November.
  • When did the invoice arrive?
  • It arrived late.
  • The invoice, which was late, missed the deadline for November accounts payable.
  • The invoice was late, so we could not include it in November accounts payable.
  • Next time, send us the invoice promptly.
  • What happened with the late invoice was that we could not include it in in November accounts payable.
In some cases, parts of the sentence are understood but not stated:
  • Too late. (The invoice was too late.)
  • Late again! (The invoice was late again!)

These examples reveal several things about sentences.

  1. First, they are self-contained, although they might rely heavily on something said earlier (or later) for readers to fully comprehend them.
  2. Second, they consist of a meaningful word or group of words.

A word constituting a sentence does not have to be a particular kind of word, nor does it have to be meaningful in normal contexts.

OK and Yes are clearly self-contained expressions, but String could also be a sentence:

  • What did you use to secure the box?
  • String. (I used string. [The “I used” is understood.])
Single verbs can also function as sentences:
  • What do you suggest I do during lunch?
  • Run. (I suggest that you run.)
So, must sentences express complete thoughts to be sentences?

Yes, although the completeness of the thought usually depends on the context in which the sentences appear. For an utterance to be a sentence, it must either state or imply a complete thought, given its context.

Must sentences contain a subject and a verb to be sentences?

“Yes” and “No”.

Sentences do have a grammatical structure, including a subject and a verb, but either or both can be understood:
  • When should I leave?
  • Now. (“You should leave” now.)

    In this particular sentence, the subject (you) and the verb (should leave) are both understood.

Sometimes the subject and/or verb are complicated and don’t convey the primary meaning or central thought in the sentence:
  • What happened with the late invoice was that we could not include it in November accounts payable.

The subject is What happened with the late invoice. The verb is was.

The subject is a complicated noun clause, and the main meaning is not in the main verb, but in the final clause: that we could not include it in November accounts payable.

Still, in most business and technical writing, sentences do have a subject and verb, even if these grammatical slots are filled with many words and have complex grammatical relationships.

Perhaps because sentences are difficult to define, most grammar handbooks settle for two fairly simple yet practical systems for cataloguing sentences:

Purpose or IntentGrammatical Structures
  1. Declarative SentencesOpens in new window
  2. Interrogative Sentences
  3. Exclamatory Sentences
  4. Imperative Sentences
  1. Simple Sentences
  2. Compound Sentences
  3. Complex Sentences
  4. Compound-Complex Sentences

1.  Purpose or Intent of Sentences

1.1  Use declarative sentences to make statements of fact and opinion.

Usually such sentences follow the subject-verb word orderOpens in new window, and they end with a period:

  • We reviewed the report.
  • Because of the detailed analyses involved, our review of the report is likely to take several days.
  • The report is only five pages long.
  • The report, which is only five pages long, will still take several days to review because the analyses are lengthy.
1.2  Use interrogative sentences to ask questions.

Interrogative sentences usually begin with a question word (who, which, where, when, why, what, and how) or with a verb:

  • Who is the engineer in charge?
  • Which plan is likely to be approved?
  • When will the construction project end?
  • How often do they propose to inspect the site?
  • Have you filled in all the necessary forms?
  • Were the construction specifications adequate?
1.3  Use exclamatory sentences to make strong assertions or surprising observation.

Exclamatory sentences usually end with an exclamation mark:

  • What a surprising conclusion!
  • That’s wrong!
  • What a field day for the lawyers that will be!
  • Oh, I doubt that!

NOTE: Exclamatory sentences often have grammatical structures very different from normal declarative sentences. In fact, they may be only a word or two long:

  • No!
  • How surprising!
  • A shame!
1.4  Use imperative sentences to give directions or commands.

Imperative sentences usually begin with a verb and end with a period (although an exclamation mark is also occasionally possible):

  • Check the Internet for additional information.
  • Adjust the flange on the steam connection to prevent leakage.
  • Do not submit the pink copy of this form!
  • Stop. (or stop!)

2.  Grammatical Structures of Sentences

Sentences have four grammatical structures—simple, compound, complex, and compound-complex. These four structures, however, can be formed into an infinite number of unique sentences.

2.1   Simple Sentences

Simple sentences are sentences that express one complete thought.

Essentially, simple sentences contain a single subject and a single a verb, although both subject and verb may be compound:

  • The pump failed. (single subject and verb)
  • The new steam pump failed after only 3 weeks of service. (single subject and verb)
  • We analyzed the blueprints. (single subject and verb)
  • James Hawkins and I analyzed the blueprints for the new maintenance facility. (compound subject, single verb)
  • James Hawkins and I analyzed and revised the blueprints for the new maintenance facility. (compound subject and compound verb)

NOTE 1: As indicated above, simple sentences can contain compound subjects, such as James Hawkins and I, and compound verbs, such as analyzed and revised. Although compound, such subjects and verbs form a single unit, at least for the purpose of the sentence in question, so the sentence is still considered simple.

NOTE 2: A quick test for a simple sentence is that you cannot logically break the sentence at any point and come up with two other simple sentences. For example, the following simple sentence, even with compound subject and compound verb, cannot be broken into two simple sentences, so the sentence is a single, simple unit:

  • My supervisor and I joked about the assignment and then worked on ways to accomplish it.

2.2   Compound Sentences

Compound sentences are a union of two or more simple sentences.

These simple sentences are usually linked by one of the simple coordinating conjunctions: and, but, or, nor, for, yet, and so.

  • The project was expensive, and management still hadn’t decided to proceed with it.
  • Our supervisor wanted to increase office productivity, but the turnover in personnel made such an increase unlikely.

Sometimes the simple sentences are linked by a semicolon or by a semicolon and a conjunctive adverb:

  • The data confirmed our initial assumptions about the problems in prototype production; with these problems, the project will almost certainly exceed the budget.
  • The surveying was to have been completed by October 15; however, construction must start on or before November 15.

NOTE 1: A quick test for a compound sentence is to see if you can divide the sentence into two or more simple sentences:

  • The surveying was to have been completed by October 15. Construction must start on or before November 15.

NOTE 2: Sometimes three or more simple sentences can combine into a compound sentence:

  • The site was ready, the construction crew was ready, and the materials were ready, but the weather was not cooperative.

2.3   Complex Sentences

A complex sentence is a simple sentence with a dependent (subordinate) clause attached to it.

The dependent clause can appear before the main clause (the otherwise simple sentence), in the middle of the main clause, or following the main clause. Here are some dependent clauses:

  • Although our bid was the lowest …
  • … who was the most expensive candidate …
  • … because the tailings pile is virtually inert.

Adding a simple sentence to each of these dependent clauses forms a complex sentence:

  • Although our bid was the lowest, another contractor had more experience.
  • Cameron Blake, who was the most expensive candidate, did have the most impressive credentials.
  • Reclamation of the mine site will be difficult because the tailings pile is virtually inert.

NOTE 1: A test for a complex sentence is to separate the dependent clause and the main clause (simple sentence). This test will work for the sentences above, but not for this sentence:

  • What Jack wanted to discuss with us became clear once the meeting got under way.

    What Jack wanted to discuss with us is a noun clause that functions as the subject of the sentence. Trying to separate it from the rest of the sentence would result in two sentences fragments, neither of which can stand alone. Although this sentence fails the test, it is still a complex sentence.

NOTE 2: Dependent clauses are usually introduced by these words:

Subordinate conjunctionsBecause, since, although, even though, after, before, so that, while, when, etc. See Subordinate ConjunctionsOpens in new window.
Relative pronounsWho, whom, whose, which, that, whoever, whomever, why, when, where, etc. See Relative PronounsOpens in new window

2.4   Compound-Complex Sentences

Compound-complex sentences are a combination of the two previous sentence types. They are both compound and complex.

Therefore, a compound-complex sentence has two attached independent clauses—a compound attached to each other)—and at least one independent clause:

  • Because the firm’s manufacturing capacity could not be increased rapidly enough, they were unable to fill their orders; consequently, competitors, gained a significant foothold on the market.

NOTE: Because this sentence is compound, the semicolon separates two independent clauses, each of which could stand alone as a complete thought. The introductory dependent clause beginning with because makes the sentence complex.

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  • References
    • FranklinCovey Style Guide: For Business and Technical Communication Sentences (Pg 282–285) By Stephen R. Covey.

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