When a sentence lists or compares ideas, those ideas have to be dressed in the same grammatical 'uniform.' Mismatched forms are an easy trap the test loves — and an easy point once you can spot them.
Parallel structure (also called parallelism) means that items doing the same job in a sentence should share the same grammatical form. If you're listing, comparing, or pairing things, they all need to look alike.
Think of it like a sports team: everyone in the lineup wears the same jersey. If three players show up in jerseys and one shows up in a tuxedo, something's off.
There are three main places parallelism shows up on the test:
1. Lists (three or more items)
Every item in a list should be the same part of speech or form.
❌ She likes hiking, swimming, and to bike.
✅ She likes hiking, swimming, and biking.
Notice the fix: all three end in -ing. The odd one out (to bike) was the tuxedo.
2. Paired items joined by a conjunction
Words like and, or, but connect two things that should match.
❌ The job requires patience and to be organized.
✅ The job requires patience and organization. (two nouns)
3. Comparisons
When you compare two things, the test often hides parallelism in the comparison. The thing on each side of the comparison must be the same kind of thing — and you may need a placeholder word like that or those.
❌ The scores of the first group were higher than the second group.
✅ The scores of the first group were higher than those of the second group.
Here you're comparing scores to scores, not scores to a group. The word those stands in for "the scores," keeping the comparison parallel.
How to spot it on the test: When you see a list, a pair joined by and/or, or a comparison word (than, as, compared with), check that the connected pieces match in form. Pick the answer choice that makes them match. You don't need to name the part of speech — you just need them to be consistent with each other.
Parallelism questions reward pattern-matching. Find the items being joined, look at the form of the ones that are already correct, and choose the answer that follows the same pattern.
Choose the option that completes the sentence following the conventions of Standard English:
The internship taught Maria how to analyze data, write clear reports, and _______ to a professional audience.
Choose the option that completes the sentence following the conventions of Standard English:
The researchers found that the migration patterns of the coastal birds were more predictable than _______ inland birds.
In comparisons, students compare a thing to the owner of the thing (scores to a group, patterns to birds). Always ask: what noun is on the left side? The right side must be that same noun — often signaled by that (singular) or those (plural).
An answer choice can mean the right thing but be the wrong grammatical form. 'Hiking, swimming, and to bike' all describe activities, but the forms don't match. Check the form (verb? noun? -ing?), not just the idea.
Phrases like 'the presentation of findings' sound sophisticated but break the pattern. Parallelism usually favors the simplest choice that matches the other items, not the wordiest one.
Use that for a singular noun and those for a plural noun. Matching the wrong number is a classic trap (e.g., 'that of the inland birds' when the noun is the plural patterns).
Items in a list, pairs joined by and/or/but, and comparisons must share the same grammatical form.
To fix a list, copy the form of the items that are already correct.
In comparisons, use 'that' (singular) or 'those' (plural) to stand in for the repeated noun so both sides match.
Match the form, not just the meaning — and don't reflexively pick the longest choice.