Two or more parts of a sentence are said to be parallel when they have the same grammatical structure.
Balancing a Sentence
If you lost one of several black buttons from your coat, you would probably not replace it with a red button. A sense of proportion and harmony, a sense of balance, would tell you to use a button like the one you lost. In like manner, parts of a sentence that have the same thought value or function should balance; they should be in the same grammatical form.
Example: I came, I saw, I conquered.
The famous words of Julius Caesar would not have nearly the impact they do had he said, “I came, I was seeing, I wanted to conquer.” The coming, the seeing, and the conquering all have the same importance in his statement. They all serve the same function. Because identical grammatical forms were used for each (simple past tense verbs--came, saw, conquered), the sentence balances; it is parallel.
Look at the following examples and notice the lack of balance in the original sentences and the sense of balance or parallelism in the corrected versions.
Faulty: I like to swim and hunting.
(To swim and hunting serve the same function in this sentence.)
Corrected: I like swimming and hunting. OR I like to swim and to hunt.
Faulty: The president has the power, the means, and should end poverty in America.
Corrected: The president has the power and the means to end poverty in America.
(Power and means are both nouns; should end, a verb phrase, does not match the list, so must be handled differently.)
Faulty: The class is not always worthwhile or a challenge.
(Worthwhile is an adjective; challenge is a noun.)
Corrected: The class is not always worthwhile or challenging.
(Both ideas are now expressed in descriptive words.)
Faulty: I hoped that my family would arrive safely and to enjoy each other’s company.
(Sentence mixes an idea introduced with that and a to phrase.)
Corrected: I hoped that my family would arrive safely and that we would enjoy each other’s
Using Conjunctions for Parallel Structure
You might notice in all the above sentences that connecting words like and and or have been used to link the parallel parts. Other conjunctions besides and and or (nor, for, so, yet, but) are equalizers, pulling together ideas, thoughts, and expressions that are equally important. Therefore, those equal ideas and thoughts need to be expressed in equal or similar patterns.
Sometimes, two words work together as coordinators to connect similar ideas:
both ........................................ and
either ......................................... or
not only ........................... but also
not ........................................... but
whether ..................................... or
Examples: Both swimming and running are great forms of exercise.
For her birthday, she would like not only a day off but also a shopping spree.
With these pairs of coordinators, make certain the word or phrase that follows each of the two coordinators is of the same kind.
Parallel Structure in Lists
Another sentence pattern that needs parallel construction is one that introduces a list with numbers or letters (sometimes used in research or business writing):
Example: The committee researched the following areas: 1) how the faculty reacted to the proposal, 2) how the students responded on the questionnaires, and 3) what the school board recommended.
NOTE: As in the above sentence, usually words like conjunctions (that, what, how, because), prepositions (of, in, by), and other introductory words need to be repeated to reinforce a parallel construction; however, with shorter parallel groups, it is not always necessary.
Examples: The troops traveled by land, by sea, and by air.
The troops traveled by land, sea, and air.
Other Examples with Parallel Structure
Sentences that express comparisons or contrasts should also be phrased in similar or balanced patterns. Usually, words like than, as, or as well as are used to connect these ideas:
Examples: It is easier to get up on a bright, sunny day than on a dreary, rainy day.
The parents were attempting to teach their children the joy of giving as well as of receiving gifts.
Writing sentences with parallel structures creates balanced and easy-to-read expressions. Using the fill-in-the-blank method and visualizing your sentence to remind yourself of those parts which need to be expressed in similar patterns are the best ways to maintain consistent parallelism in your writing.