What are parallel sentence structures?

Parallel sentence structures, or parallelism is the principle of expressing similar ideas in a similar or parallel way.

Parallelism appears in the list of Top Twenty under error #10, Faulty Sentence Structure. In previous posts, we discussed other structure errors such as fragments, run-ons, and comma splices. There are additional faulty sentence structures can jar readers and be ungrammatical in Standard English, including misplaced or dangling modifiers and incomplete or illogical comparisons.

The strictest kind of parallelism is between words, phrases, or clauses that belong to the same word class, such as noun, prepositional, or adjectival.

Let’s take some familiar quotes.

Which is the quotation attributed to Caesar ?

“I came, I saw, and conquest took place.”


“I came, I saw, and I conquered.” 

Which word did Shakespeare write for Hamlet?

“To be or not being, that is the question.”


“To be or not to be, that is the question.”

The answer for both is the second version, which consists of parallel construction.

Look at how those versions are constructed with parallel elements:

Caesars’s “I came, I saw, and I conquered.” Consists of all active verbs in the past tense and not the passive construction of “conquest took place.”

In Shakespeare’s “To be or not to be” both elements are infinitive phrases, not a mix of infinitive (to be) with a gerund (being).

Here’s another example of parallel construction using infinitive phrases:

My parents promised to buy a new car and to let me drive it.

For parallelism, each item in the construction should be the same class or pattern; it doesn’t matter which pattern you use at the beginning as long as you follow through with the same pattern.

In this example, All our neighbors are kind, friendly, and give help, the third item is not in the same form – it is not an adjective like kind and friendly but rather a verb phrase.

To give the sentence parallel construction, it should be rewritten using an adjective as the last item: All our neighbors are kind, friendly, and helpful.                                                    (above examples from English 3200)

Parallelism with coordination or compound structures

As Kolln writes in Rhetorical Grammar, the parallel structure is effective with coordination, but only when the two ideas are equal. As discussed in a previous post, the purpose of coordination is to combine ideas or structures to give them equal emphasis or importance. It is achieved through the use of the coordinating conjunctions or FANBOYS (For And Nor But Or Yet So).

Kolln provides this sentence for analysis of coordination and parallel construction:

My new exercise program and going on a strict diet will give me a new shape before swim season.

Here the coordination conjunction and connects a compound subject:

My new exercise program

will give me a new shape before swim season.


going on a strict diet

But these subjects are not of the same type:  My new exercise program is a noun phrase (NP), while going on a strict diet is a gerund (verb phrase VP).

To make the sentence parallel, put the compound subject in parallel form:

My new exercise program (NP) and a strict diet (NP)


Sticking to my exercise program (VP) and going on a strict diet (VP)

(adapted from Kolln 58)

Kolln labels unparallel sentences as incorrect or ungrammatical Standard English, but these “errors” are marked so because grammar, as noted before in this blog, deals with written English, not spoken English.

Sentences with unparallel structure can feel off-balance to readers; parallelism allows us to give symmetry and elegance, as well as clarity, to our writing.

Kolln argues further that parallelism encourages us to be precise, avoiding fuzziness that occurs by combining non-parallel forms. Consider this example with unparallel verb forms:

Experts in sports medicine emphasize the importance of water intake and are recommending a half-once per day for every pound of body weight.

This sentence with compound verbs can be rewritten as a compound sentence by adding a second subject, but the structures are still not parallel:

Experts in sports medicine emphasize the importance of water intake

 , and

they are recommending a half-once per day for every pound of body weight.

Again, with compound structures the conjunction and signals that they are equal partners. Kolln asks, do they belong together as equal partners? In this case, they are not, so and is the wrong connection. Only one of the ideas should be emphasized, but because the sentence is out of context, it’s impossible to know which one the writer would emphasize. She provides two possible arrangements:

Experts in sports medicine, who emphasize the importance of water intake, are recommending a half-once per day for every pound of body weight.

Emphasizing the importance of water intake, experts in sports medicine are recommending a half-once per day for every pound of body weight. (Kolln Rhetorical Grammar 59)

Deciding which idea is more important than another is up to the writer and the intended meaning of the piece. The concept is known as subordination and is a tool for showing relationships between your ideas—something we’ll discuss further in a future post.

LeTourneau offers a less strict use of parallelism in which items are different categories but have the same function. For instance, past participles and adjectives are often coordinated because they are modifiers, as in phrase tried and true. Adverbs and adverbial prepositional phrases are also often linked because they belong to the subcategory describing the manner in which something is done: Carefully and with minute attention to the proprieties, the debutante chose her next spoon. (English Grammar 265)

Citing the definition and examples of Edward P.J. Corbett, Kolln illustrates the use of parallelism in the rhetorical device of antithesis, or “the juxtaposition of contrasting ideas”:

“That’s one small step for a man, one giant leap for mankind. (Neil Armstrong, 1969 moonwalk)

“There never was a good war, or a bad peace.” (Benjamin Franklin, 1783 letter) (224-225)

The two quotes above also demonstrate a principle of parallelism: if the same form repeats in a construction, it can be omitted as long as the words are common to both parts of the compound structure.

A tree can stand a strong wind because it is flexible and because it has deep roots.

A tree can stand a strong wind because it is flexible and has deep roots.

Using parallel sentence structures or parallelism is an effective rhetorical tool to make your writing balanced and streamlined, giving your sentence smoothness and clarity.

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