Overview
Parallel structure (parallelism) is the grammatical convention that items joined in a list, series, or paired conjunction must all be in the same grammatical form. The Digital SAT tests parallelism in three main contexts: lists connected by coordinating conjunctions (and, or, but), correlative conjunction pairs (both…and, either…or, neither…nor, not only…but also), and comparative constructions (faulty comparisons). Approximately 1–2 questions per exam test this skill, making it one of the more predictable and learnable Standard English Conventions topics.
Key Points
4.1 The Core Rule: Matching Grammatical Form
When two or more items are joined by a conjunction (coordinating or correlative), every item must be in the same grammatical form — same part of speech, same verb form, same phrase type.
Core principle: [Item 1 in Form X] and/or [Item 2 in Form X] and/or [Item 3 in Form X]
Common forms that must stay consistent:
| Form | Examples |
|---|---|
| Gerund (-ing noun) | running, swimming, reading |
| Infinitive phrase | to run, to swim, to read |
| Bare verb (simple) | run, swim, read |
| Noun phrase | a long run, a swim session |
| Adjective | fast, efficient, reliable |
| Prepositional phrase | in the morning, at noon, in the evening |
4.2 Parallelism in Lists (Coordinating Conjunctions: and, or, but)
When three or more items appear in a list, all must share the same grammatical form. Identify the form of the non-underlined items, then match the underlined item to that form.
| Wrong (Mixed Forms) | Right (Consistent Form) |
|---|---|
| She likes running, to swim, and bikes. | She likes running, swimming, and biking. (all gerunds) |
| Her interests are painting, to sculpt, and design. | Her interests are painting, sculpting, and designing. (all gerunds) |
| He entered the room, sat down, and was opening his notes. | He entered the room, sat down, and opened his notes. (all simple past) |
| The speech was long, boring, and without meaning. | The speech was long, boring, and meaningless. (all predicate adjectives) |
Strategy: Before answering, find the items in the list that are NOT underlined. Determine their grammatical form. Choose the answer that matches that form.
4.3 Correlative Conjunctions — The Four Pairs
Correlative conjunctions are paired linking words that join grammatically equal elements. The form following the first conjunction must match the form following the second conjunction.
| Pair | Structure |
|---|---|
| both … and | both [X] and [X] |
| either … or | either [X] or [X] |
| neither … nor | neither [X] nor [X] |
| not only … but also | not only [X] but also [X] |
Examples:
| Wrong | Right | Error Type |
|---|---|---|
| She is not only intelligent but also works hard. | She is not only intelligent but also hardworking. | adjective vs. verb phrase → adjective + adjective |
| Either we go to the mall or going to the park. | Either we go to the mall or we go to the park. | full clause vs. gerund phrase → clause + clause |
| Neither the CEO nor was the board informed. | Neither the CEO nor the board was informed. | noun vs. verb phrase → noun + noun |
| Both the results were impressive and how fast they arrived. | Both the results and the speed of their arrival were impressive. | noun vs. noun clause → noun + noun |
The “not only…but also” rule in detail:
- The part of speech after “not only” must match the part of speech after “but also.”
- Tense and aspect must also match, not just the basic part of speech.
- Wrong: “Not only has she run five miles, but she is also cycling ten.” (perfect vs. progressive)
- Right: “Not only has she run five miles, but she has also cycled ten.” (both present perfect)
4.4 Comparative Parallelism (Faulty Comparison)
When a sentence compares two things using “more than,” “less than,” “-er than,” or “as…as,” both sides of the comparison must be the same grammatical and logical type. This is the trickiest subset of parallelism.
The core error: comparing a thing to a person, place, or different type of thing.
| Wrong (Faulty Comparison) | Right (Logical Parallel) | What Changed |
|---|---|---|
| The cost of living in New York is higher than Los Angeles. | The cost of living in New York is higher than that in Los Angeles. | cost vs. cost (not cost vs. city) |
| His paintings are more famous than Van Gogh. | His paintings are more famous than Van Gogh’s. | paintings vs. paintings (not paintings vs. person) |
| Mozart’s compositions were more complex than Beethoven. | Mozart’s compositions were more complex than Beethoven’s. | compositions vs. compositions |
| The rules in China are stricter than America. | The rules in China are stricter than those in America. | rules vs. rules (not rules vs. country) |
Fix options for faulty comparisons:
- Add a possessive (‘s or s’): “Van Gogh’s”
- Use “that of” (singular) or “those of” (plural): “that of Los Angeles,” “those of America”
- Repeat the noun explicitly: “the cost of living in Los Angeles”
4.5 Recognizing Parallelism Questions on the Digital SAT
Signal words that indicate a parallelism question:
- Lists: commas separating items + “and” or “or” before the last item
- Correlative pairs: seeing “both,” “either,” “neither,” “not only” in the passage
- Comparisons: “more than,” “less than,” “as…as,” “-er than,” “compared to”
The underlined portion will typically be the last item in a list or the second half of a correlative/comparative pair. The correct answer matches the grammatical form already established by the non-underlined items.
Pitfalls and Common Mistakes
Pitfall 1 — Mixing Gerunds and Infinitives in a List
Wrong: The program aims to reduce costs, improving efficiency, and it will increase output. Right: The program aims to reduce costs, improve efficiency, and increase output. (all bare infinitives after “to”)
Fix: Identify the first item’s form. Here, “reduce” is a bare infinitive following “to”; all items must be bare infinitives. Change “improving” to “improve” and remove “it will increase.”
Pitfall 2 — Mismatched Forms in “Not Only…But Also”
Wrong: She is not only a talented musician but also composes her own songs. Right: She is not only a talented musician but also a prolific composer. (noun phrase + noun phrase) OR: She not only plays music but also composes her own songs. (verb phrase + verb phrase)
Fix: What follows “not only” sets the form. If a noun phrase follows “not only,” a noun phrase must follow “but also.” If a verb follows “not only,” a verb must follow “but also.”
Pitfall 3 — Faulty Comparison: Comparing a Thing to a Person or Place
Wrong: The research methods used by this team are more rigorous than other scientists. Right: The research methods used by this team are more rigorous than those of other scientists.
Fix: Check both sides of “than” or “as…as.” Are you comparing the same type of thing? If one side is “methods” and the other is “scientists,” add “those of” to make it “methods vs. methods.”
Pitfall 4 — Parallel Structure Across Long Distances
Wrong: The committee voted to increase funding for education, to propose new housing initiatives, and a plan to reduce carbon emissions was also considered. Right: The committee voted to increase funding for education, to propose new housing initiatives, and to consider a plan to reduce carbon emissions.
Fix: In longer sentences, the parallelism error can be buried by distance. Always read the full list from start to finish and verify every item matches in form, even if items are long clauses.
Pitfall 5 — Adjective vs. Prepositional Phrase
Wrong: The lake is wide, deep, and of a great length. Right: The lake is wide, deep, and long. (all simple adjectives)
Fix: “Of a great length” is a prepositional phrase; the other two items are adjectives. Convert the prepositional phrase to its adjective equivalent.
Related Entries
- Modifier_Placement
- Sentence_Boundaries
- Verb_Tense_Voice_Mood
- Punctuation_Commas
- Pronoun_Antecedent_Agreement
Quick Reference Card
| Context | Signal Words | Core Rule | Fix |
|---|---|---|---|
| List / Series | and, or, but | All items must share the same grammatical form | Match the form of the non-underlined items |
| both…and | ”both” | [X] and [X] — same form on each side | Make the element after “and” match the element after “both” |
| either…or | ”either” | [X] or [X] — same form on each side | Make the element after “or” match the element after “either” |
| neither…nor | ”neither” | [X] nor [X] — same form on each side | Make the element after “nor” match the element after “neither” |
| not only…but also | ”not only” | [X] but also [X] — same form, same tense/aspect | Match part of speech AND tense on both sides |
| Faulty comparison | more than, -er than, as…as | Compare same type of thing | Add “those of,” “that of,” or possessive to align the comparison |
The Parallelism Check:
- Find the conjunction or signal word (and / or / both…and / not only…but also / more than).
- Identify the grammatical form of the item(s) you cannot change (non-underlined).
- Select the answer that matches that form exactly — same part of speech, same verb form, same phrase type.