Sentence Structure

When building anything, you should be familiar with the tools you are using. Grammatical elements are the main “tools” you use 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 (governed by a noun or pronoun) and the predicate (or verb phrase, governed by a verb). The subject refers to the topic being discussed, while the verb phrase conveys the action or state of being expressed in the sentence.

All clauses must contain both a subject and a verb. Phrases, on the other hand, lack a subject or a verb, or both, 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. All sentences contain at least one independent clause. Dependent clauses, also called subordinate clauses, rely on another part of the sentence for meaning and can’t stand on their own. These clauses are often the most common types of sentence fragments that students write.

Consider the examples below.

Example 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.^[1]

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.

Compound sentences have two or more main clauses joined by coordinating conjunctions (CC) such as “for,” “and,” “nor,” “but,” “or”, “yet,” and “so” (FANBOYS). You can also connect them using punctuation such as a semi-colon or a colon. By coordinating the ideas, you are giving them roughly equal weight and importance.

• Subject + verb, CC Subject + verb

The following are all compound sentences. Any conjunctions are indicated in bold.

Complex sentences express complex and usually unequal relationships between ideas. One idea is “subordinated” to the main idea by using a “subordinating conjunction” (such as “while” or “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 sentence 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.

• Subordinating Conjunction + subject + verb (this is the dependent clause), Subject + verb (this is the main clause)

The following are all examples of complex sentences. The subordinating conjunctions are in bold.

Here is an example of a complete sentence followed by a subordinate clause fragment.

To correct this error, add the subordinate clause to the complete sentence to form a single sentence.

You could also try the following:

Compound-complex sentences contain at least two independent 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. Each of the sentences below is a compound-complex sentence:

Using Rhythm to Construct Sentences

When thinking about sentence structures in your writing, you will also want to focus on another major concept closely related to structure and clarity: rhythm. Similar to the notes and rests in a piece of sheet music, the words and punctuation of a document or speech can be understood as intentional combinations of sound and silence, designed to create a particular effect beyond the content of the page. On the sentence level, rhythm can not only help readers understand and recall content, but also help writers amplify its meaning and importance.

Rhythm is what makes reading aloud an effective means of catching grammatical and mechanical mistakes. When we write and read silently, we cannot hear the innate rhythm of words the way we can in speech. Here are some common examples of faulty grammatical and syntactical rhythm to avoid:

Fragments. Sentence fragments are incomplete sentences that lack an independent clause. These can make your writing sound choppy or stilted. Fragments can typically be corrected by combining the fragment with another sentence or rephrasing it as an independent clause.

Run-ons. These occur when multiple subjects and clauses are put into one sentence without any punctuation to provide breaks. Run-ons obscure important shifts in thought/focus on the sentence level; these shifts help the reader anticipate and process the flow of your content. To avoid sentences like this, it helps to identify any independent clauses and assign them their own sentences.

Repetitive sentence beginnings. Starting multiple sentences in a row with the same word (or even the same sound) will create a monotonous, list-like rhythm. This happens most often with words like “I” or that begin with “Th.” Instead, try changing up your beginnings and using harder sounds like consonants to create a more dynamic, punchy rhythm.

Repetitive sentence length. Using the same sentence type (simple, complex, compound, etc.) repeatedly creates a less engaging rhythm. Variety, as it does with sentence beginnings, draws the reader’s attention more effectively.

The Known-New Principle. This concept is also known as the Old/New Contract. Readers typically find it helpful when writers use familiar information to introduce new information or terms, so that they can use their prior knowledge to make connections that demystify the new material. This is true on both the paragraph and sentence levels. Maintaining this rhythm of known and new information thus creates a natural progression of content.

Commas

Often, students are only vaguely taught how to use commas. They are told to “put it where it feels right,” “put it where you take a break in the sentence,” or other similarly unhelpful advice. For those who like more structured rules, this can be frustrating.

If you comprehend the different sentence and clause types presented earlier, however, there are actually a handful of comma rules that apply to most situations. As with many other writing conventions, these are rules appropriate to formal, academic, technical, or business writing—they don’t necessarily apply to creative writing or dramatic writing in the same way.

After a discussion of commas, this chapter ends with a brief guide to many other common types of punctuation—from the period, to the semi-colon, to the difference between a hyphen and a dash.

Commas

These nine rules and a list of additional miscellaneous instances cover the majority of the times you will need a comma. You will notice that some of them even overlap a bit.

1. Before a coordinating conjunction joining two independent clauses..
   Separate two independent clauses with a comma plus a coordinating conjunction. English has seven coordinating conjunctions. One way to remember them is with the acronym FANBOYS (For, And, Nor, But, Or, Yet, So). In the following examples, both the coordinating conjunction and comma connecting the two independent clauses are in bold. 

Note: Don’t confuse two Independent clauses with a single subject/compound verb.

2. Dependent clause, independent clause.
   When the dependent clause comes first, separate it from the independent clause with a comma, but not the other way around. In the examples below, the dependent clause is in bold.

3. After a long introductory phrase.
   Place a comma between long introductory phrases and an independent clause. These are most often prepositional phrases. Handbooks tend to disagree about what makes an introductory phrase “long”; however, Table 5.12 offers some suggestions.
   

Table 5.12. Introductory phrases and commas.

4. Items in a series.
   Separate items in a series of at least three with commas; the comma before the final “and” is optional and called the “Oxford comma” or the serial comma. Whether you choose to use the serial comma or not, be consistent throughout your document. 

5. Coordinate adjectives.
   Use a comma between coordinate adjectives not linked by a coordinating conjunction. Coordinate adjectives are separate words that modify a noun rather than a compound adjective, which is a single modifier that is composed of two words. If you’re unsure whether you are using coordinate adjectives, try 1) reversing the order of the adjectives and 2) placing “and” in-between the adjectives. If the sentence’s meaning has not changed, you are likely using coordinate adjectives.

Exceptions: Colors, nouns acting as adjectives, old/young, (and additional random adjectives

6. Non-restrictive relative clauses.
   A relative clause is a clause that begins with a relative pronoun such as “who,” “which,” or “that.” Non-restrictive relative clauses offer nonessential, parenthetical information, and are thus bracketed by a pair of commas. Restrictive clauses, in contrast, use no commas because the information they provide is essential to the meaning of the sentence.

Whether a phrase is restrictive or not depends on context and the audience’s knowledge.

7. Appositives (non-restrictive phrases).
   Appositives rename/describe the noun they come after. Since these phrases are non-restrictive and do not contain essential information, they should be set off with a pair of commas.
   

8. Parentheticals.
   Set off parenthetical comments, often transitional words, with a pair of commas. In the examples below the parenthetical phrase and commas are in bold.
   

9. Participial phrases.
   Separate a participial phrase from the independent clause with a comma whether it appears before or after that clause. Participial phrases usually describe “background” actions and feature an -ing verb; commas help to distinguish these actions from the main action of the independent clause. Be careful not to have a “misplaced modifier” or “dangling participle” with this type of sentence construction. Make sure the subject of the sentence is the person doing the action of the participle.

Other Comma Guidelines

Use a comma whenever clarity demands it. For instance, use a comma here, even though the introductory phrase is short, because otherwise the sentence is a little more difficult to read.

Use a comma (before and) after all transitional phrases/words.

Use a comma after interjections. Interjections include such words as “Well,” “Yes,” or “No.”

Use a comma to mark direct address.

Separate contrasting elements with a comma. This rule means that sometimes you use a comma before “but” even though it is not between two independent clauses.

Use a comma to separate days, dates, and years.

Use a comma to separate streets, cities, and states.

Always remember the most important rule of comma use: commas, like all parts of technical writing, are primarily about reader comprehension and the impression you make on your audience. Use commas for clarity in these places, but keep in mind that readability is the most important aspect.

Punctuation Other than Commas

1. .
   Period/Full Stop. The most common form of end punctuation.
   • Used at the end of complete sentences.
   • Used at the end of abbreviations.
   • Goes inside the quotation marks if there is no citation, or after the parenthesis if there is a parenthetical citation.
2. !
   Exclamation Point/Exclamation Mark. Used to convey emphasis or surprise.
   • Should be used very sparingly! In other words, you should hardly ever use it, especially in technical and professional writing.
3. ?
   Question Mark. Used at the end of questions.
   • In English, questions are often marked not only by the question mark, but also by a rearrangement of the syntax of a sentence. Do you know what I mean?
   • Rhetorical questions can be effective, but should be used carefully, as too many can be distracting.
4. ’ and ‘ ’
   Apostrophe and Single Quotes. Used in possessives, contractions, and quotes-within-quotes. Use in the following scenarios listed below:
   • After all singular nouns that do not end in “s” and singular proper nouns that do not end in “s,” add an ’s to mark possession.

• • After singular nouns that end in “s,” add only an ’ after the “s” to mark possession.

• • After singular proper nouns that end in “s,” add an ’s at the end to mark possession.

• • After plural nouns that do not end in “s,” add an ’s to mark possession.

• • After plural nouns that end in “s,” add only an ’ after the “s” to mark possession.

• • An apostrophe can also be used to note missing letters or sounds in a contraction. Contractions are usually fine in correspondence. For the most formal situations, avoid contractions.

• • Finally, single quotation marks ‘ ’ are used when you have a quotation within a quotation.

1. “”
   Quotation Marks. Used around quotations and to mark specific types of words.
   • Always come in pairs.
   • Mark the beginning and endings of direct quotations, which are the exact words of someone else, or yourself at an earlier time, whether written or spoken.
   • Also used when a word or term is mentioned rather than used, especially when identifying a term to be defined.
2. :
   Colon. Used to show a particular relationship between the information before and after the colon or within certain types of numbers and marking systems.
   • Colons may only be used after complete sentences.
   • What comes after the colon expands on or explains what came before.
   • It has two common uses: after a complete sentence before a list and after a complete sentence before a quotation.
   • Also used in notations of time and verse/chapter references.
3. ;
   Semicolon. Used to separate independent clauses or to separate long or punctuated items in lists.
   • Semicolons can be used when two complete sentences are very closely related, especially if the second sentence begins with a conjunctive adverb such as “however” or “thus”.

• • Semicolons can also be used in lists when the items in the lists contain commas.

4. ()
   Parentheses. (A single mark is a parenthesis.) These can be used to insert side comments or to mark citations. 
   • Parenthetical statements often add clarity or humor, but are ultimately unnecessary (though they can be interesting).
   • Parentheses are also used to indicate in-text citations in MLA, APA, and some other styles.
5. . . .
   Ellipsis. (The plural is ellipses). An ellipsis indicates that something is omitted. 
   • An ellipsis marks an omission. For instance, in a quotation, if a word is left out to make it flow better or an unnecessary phrase is left out to make it more concise, an ellipsis marks where the information or words were removed.
   • An ellipsis should be three periods with spaces on either side and between, unless the ellipsis occurs at the end of a sentence, in which case there is an immediate period followed by three periods (making four periods total).
6. []
   Square Brackets. Brackets are the opposite of ellipses. They indicate that something was added or changed in a quotation.
   • For instance, when adding an article or a preposition or pronoun to make a quotation flow smoothly with the rest of the sentence, the writer adds square brackets to mark the change.
7. –
   Hyphen. Hyphens are short dashes used to combine words.
   • Hyphens are used in compound words and adjectives, indicating that the hyphenated words are to be considered one unit.
   • Some words are always hyphenated (though which words these are changes over time).

• • Compound adjectives that precede their noun are often hyphenated to show they act as a unit.

8. –
   En dash. En dashes are the medium-length line. They separate number ranges, including ranges of time.

• • When using an en dash, do not add spaces between the dash and the words or numbers it is connecting.
  • To type an en dash on Windows, use CTRL+Minus(-); on Mac, use Option+Minus(-).
  • The ALT code for the en dash is 0150.

9. —
   Em dash. The longest dash of the three can grammatically replace a comma, parentheses, semicolon, or colon. Em dashes are more emphatic than other forms of punctuation; they draw attention to the information following a dash. They are also considered less formal than the types of punctuation they replace, so use them wisely in technical and professional communication. The following examples demonstrate how the em dash may replace different punctuation marks.
   • Used as parentheses.

• • Used as a semicolon.

• • Used as a colon.

• • When using an em dash, do not add spaces between the dash and the items t replaces.
  • To type an em dash, on Windows use Alt+Ctrl+Minus(-); on Max, use Option+Shift+Minus(-). For Google Docs, you will need to insert the em dash using Insert Special Character.
  • The ALT code for the em dash is 0151.

Punctuation, like all parts of technical and professional writing, is primarily about reader comprehension and the impression you make on your reader. The rules are in place so that there is a common basis of understanding. By using correct punctuation, sentence structure, and strong verbs, you will increase clarity for your reader. Furthermore, by following the 7 Cs addressed at the beginning of the chapter, you will further increase your ethos and credibility, thus encouraging your readers to trust your professionalism and expertise.