Faulty Parallelism

Faulty parallelism is the name for an imbalance in writing. Often, faulty parallelism does not come across as an obvious grammatical mistake, but the reader is left thinking there is something wrong with the sentence and they read it again to look for the problem. This is not desirable in formal writing, as the reader should be focused on the content of the writing, not the structure.

With Prepositions

When writing a list of things, prepositions should be used accurately yet sparingly; do not repeat prepositions unnecessarily, but ensure each item in your list is properly modified.



Incorrect: The housekeeper came on Monday and then again Friday.

The parallelism of this sentence is disrupted by the words then again, which leave Friday unmodified by a preposition. The preposition on should be inserted before Friday: The housekeeper came on Monday and then again on Friday.



Incorrect: When the blender was turned on, the lid flew off and the milkshake splattered on the walls, the sink and the counter.

Generally, we do not use “on the sink” in English. This sentence may be better written as, “…the milkshake splattered on the walls and the counter, and in the sink.”

With “Either…Or”

When using “either…or”, the options given must be interchangeable, and should therefore have the same grammatical structure.



Incorrect: I really want either a puppy for my birthday, or I guess a rabbit would be nice, too.

The clauses following “either” and “or” should be interchangeable; “I really want either I guess a rabbit would be nice, too” does not make sense to the reader. This would be better written as two sentences:I really want either a puppy or a rabbit for my birthday. Both puppies and rabbits are nice.



Incorrect: Following the introduction of the new protocol, the irate employees will either be placated, or the protocol will have to be adjusted.

The clauses following “either” and “or” should be interchangeable; “The irate employees will either the protocol will have to be adjusted” does not make sense to the reader. The sentence could be re-written: Following the introduction of the new protocol, the irate employees will either be placated, or request adjustments to the protocol.

With “Not Only… But Also”

The phrases following “not only”and “but also” should be interchangeable and, therefore, should have the same grammatical structure. When these phrases are not interchangeable, it creates faulty parallelism.



Incorrect: I want to write not only stories for children, but also do the illustrations.

The phrases following “not only” and “but also” should be interchangeable. The phrase, “I want to write not only do the illustrations” does not make sense. To make this sentence understandable, one might re-arrange the words: I want not only to write stories for children, but also to do the illustrations.



Incorrect: The boys not only ate all the hot dogs and the whole salad, but also the entire cheesecake.

The phrases following “not only” and “but also” should be interchangeable. To make this possible in this sentence, the verb “ate” should be moved: The boys ate not only all the hot dogs and the whole salad, but also the entire cheesecake.

With Gerunds and Infinitives

When one has the option of using the infinitive of a verb (i.e. beginning with “to”); background: or the gerund (i.e. ending with “ing”), one must choose one or the other, depending on the tone of the sentence. Frequently, using the infinitive creates a more formal tone, while using a gerund is more common.



Incorrect: My professor thinks understanding a second language and to be able to translate the second language are inherent.

The gerund, “understanding”, and the infinitive, “to be able to translate”, should not be used in the same sentence. The sentence would be better written: My professor thinks understanding a second language and being able to translate the second language are inherent.



Correct: I wanted to go hiking and to see the waterfalls.

Because the infinitive, “to go”, is used before the gerund, “hiking”, this sentence is considered correct.

Incompatible Verb Tenses on Either Side of Co-Ordinating Conjunction

In a sentence with a co-ordinating conjunction (“and”, “or”, “nor” “but”, “so”, “yet”, and “for”), the verbs on either side of the co-ordinating conjunction should make chronological sense. Most of the time, the verbs will be in the same tense (e.g. both past tense).



Incorrect: The cafeteria has not reduced the use of sodium nor eliminates the use of MSG.

The co-ordinating conjunction “nor” has two verbs on either side: “has not reduced” and “eliminates”. The verbs do not make chronological sense. “Eliminates” should be changed to the past tense: eliminated.



Incorrect: The cafeteria claims it serves healthy food and wanted to advertise in the health food store.

The two verbs, “claims” and “wanted” do not make chronological sense. They should be changed to either the past tense (claimed; wanted) or the present tense (claims; wants).



Correct: The cafeteria has eliminated the use of animal byproducts and will introduce a vegan menu in the near future.

Even though the verbs “has eliminated” and “will introduce” are in different verb tenses, they make chronological sense; this sentence is grammatically correct.

Nonparallel Verbs With Correlative Conjunctions

Ensure the verbs used with the correlative conjunctions are parallel.



Correlative conjunctions are pairs of words like “either…or” and “whether… or”. When using correlative conjunctions, the verbs in both phrases should be parallel (i.e. they should make chronological and grammatical sense). Sometimes the verbs will need to be in the same tense (e.g. both infinitive or both simple past) and sometimes they will be in different tenses. If the verbs are in different tenses, ensure they make chronological sense.



Incorrect: To maintain good health, we not only exercise but also to eat well.

The correlative conjunction in this sentence is “not only… but also”. The verb which is used in the “not only” clause is in the simple present tense (exercise). The verb which is used in the “but also” clause is in the infinitive (to eat). The “to” should be removed from the last clause so both verbs are in the simple present.



Correct: Just as his father went to university, so will Brad go.

With a correlative conjunction like “just as… so”, different verb tenses may be used. To have one verb in the past tense (went) and one in the future (will go) is acceptable because it makes chronological sense.

Faulty Parallelism in Comparisons Using “Than”

When making a comparison by using the word “than”, the verbs on either side of “than” should be parallel. Sometimes the verbs will need to be in the same tense (e.g. both infinitive or both simple past) and sometimes they will be in different tenses. If the verbs are in different tenses, ensure they make chronological sense.



Incorrect: This white cat is more amusing than the brown cat to be.

The two verbs, “is” and “to be”, are not parallel. “To be” should be changed to past or present tense.

Correct: This white cat is more amusing than the brown cat was.

Correct: This white cat is more amusing than the brown cat is.



Incorrect: I believe Marlowe being a better playwright than Shakespeare was.

“Being” should be changed to “was” so it is grammatically parallel to the second verb “was”.



Incorrect: He was much worse at public speaking than he used to be.

The verbs in this sentence do not make chronological sense. One or both of the verbs should be changed.

Correct: He is much worse at public speaking than he used to be.

Correct: He used to be much worse at public speaking than he is (now).

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