Faulty Parallelism

When you list two or more things in a sentence, your reader expects them to arrive in the same shape — like matching train carriages coupled together. When one item breaks the pattern, the sentence gives a little jolt, and even a reader who could not name the problem feels that something is off. That jolt is faulty parallelism: a list whose items do not share a matching form.

This is one of those errors that is far easier to hear than to explain, and far easier to make than you would think. It creeps in most when you are writing quickly and the ideas arrive in slightly different grammatical clothes. The cure is not complicated, but it does require a habit: before you finish a list, glance back and check that every item is built the same way. Do that, and your sentences stop stumbling and start to flow.

The rule: matching shapes

Every item in a list should be the same kind of word or phrase — all -ing words, or all "to" verbs, or all nouns, or all adjectives. Mix the shapes and the list wobbles:

✗ I like swimming, running and to cycle. ✓ I like swimming, running and cycling. (all -ing)

✗ The job needs someone patient, kind and who works hard. ✓ The job needs someone patient, kind and hard-working. (all adjectives)

The meaning barely changes between the wrong and the right version. What changes is the balance — and balance is what makes a list easy to read.

Where it sneaks in

Faulty parallelism has a few favourite hiding places. It loves lists of three, and it especially loves the paired structures not only… but also, either… or, and both… and, where the two halves must match each other exactly:

✗ She is good at maths, science and playing the piano. ✓ She is good at maths, science and music. (three nouns)

✗ He not only scored but also the assist. ✓ He not only scored but also assisted. (both verbs)

A useful way to picture the paired structures: whatever kind of word comes straight after not only must be echoed by the same kind of word straight after but also. If the first is a verb, the second must be a verb too.

The fix: line them up

The repair is always the same. Read your list back and check whether each item is the same type of word or phrase. Find the odd one out — there is usually just one — and reshape it so it matches the others. Often the neatest fix is to swap a whole clause for a single word (who works hard → hard-working), or to change a verb's ending so it lines up (to cycle → cycling).

A second angle: the "say the stem again" test

Here is a quick test that catches almost every parallelism slip. Find the part of the sentence that leads into the list — the stem — and then say it silently before each item in turn, as if starting a fresh little sentence each time. Take I like swimming, running and to cycle. The stem is I like. Now try it against each item: I like swimming (good), I like running (good), I like to cycle (also grammatical on its own, but listen — it does not match the shape of the first two). The moment one item forces you to change gear, you have found the odd one out. This works because a good list is really just the same stem sprouting several matching branches. If every branch grows the same way from the stem, the list is parallel; if one branch twists off in a different direction, that is the one to reshape. Run this test on any list you are unsure about and the faulty item almost announces itself.

An edge case: keep the little words consistent too

Parallelism is not only about the big words; the small linking words in front of a list need to be handled evenly as well. You have two tidy choices: use the linking word once, in front of the whole list, or repeat it in front of every item — never just some.

✗ You can travel by bus, car and by train. ("by" appears twice, but not before "car") ✓ You can travel by bus, car and train. (one "by" for the whole list) ✓ You can travel by bus, by car and by train. ("by" before every item)

Both corrected versions are balanced; the faulty one is lopsided because by is there for some items and missing for another. The same goes for words like to, the, and a at the start of list items: all in, or one out front — but never a random mix.

Why it matters

Faulty parallelism is a classic marker of writing that has not been checked, which is exactly why examiners notice it — a balanced list signals a writer in control of their sentences. But the deeper reason to care is clarity: matching shapes let your reader take in a list at a glance, grouping the items together instead of tripping over the one that does not fit. In persuasive writing and speeches, balanced lists are also more memorable, because the repeated pattern gives them rhythm. So fixing parallelism does two jobs at once — it removes an error and it makes your writing land harder. And the check takes only seconds: run your eye down the list and make every carriage match.

Quick check

Fix the odd item out in each list:

1. We spent the day swimming, sunbathing and we played volleyball.

2. The recipe is quick, cheap and it tastes good.

3. She likes to sing, to dance and drawing.

4. He is not only clever but also works hard.

Where next

• Uneven Lists and Comparisons — the common-errors angle.
• Parallelism and Balance — building balanced sentences.
• Commas in Lists — punctuating the list.