5 Small Writing Mistakes Grammarly Catches That Non-Native Writers Miss Every Time

TL;DR: The mistakes that make non-native writing feel slightly “off” are rarely big grammar errors — they’re small, high-frequency slips like articles, prepositions, and subject-verb agreement. These are exactly the errors that are hardest to self-edit, because they’re about how a language feels rather than a rule you consciously apply. Here are five Grammarly’s free plan reliably catches.

Why Listen to Me on This

I proofread a lot of formal writing — reports and emails — in a language that isn’t my first, and I run finished drafts through Grammarly’s free version as a second check before sending. Over time, the same handful of error types keep showing up in the suggestions, regardless of how carefully I think I’ve already checked the document myself. This list is built from that pattern, not a general feature tour.

1. Articles (a / an / the)

Missing or misused articles are probably the single most common flag for non-native writers, and they’re also the easiest to miss when you re-read your own writing — your brain fills the gap automatically because you already know what you meant. A sentence like “I attended meeting yesterday” reads as complete to the writer and incomplete to a native reader. Grammarly’s free plan catches these consistently, and they’re usually one-click fixes.

2. Prepositions

“Interested on” instead of “interested in,” “discuss about” instead of “discuss” — preposition pairings in English are largely arbitrary and don’t translate cleanly from most other languages. There’s no shortcut to memorizing all of them, which is exactly why an automated second check is useful here: it’s a high-volume, low-stakes category of error that’s tedious to self-audit but quick to fix once flagged.

3. Subject-Verb Agreement

This one gets slippery specifically in longer sentences, where the subject and verb are separated by a clause or two — by the time you reach the verb, it’s easy to lose track of whether the subject was singular or plural. It’s a mistake native writers make too, but it shows up more often in non-native writing because there’s less automatic “that sounds wrong” instinct to catch it before you finish typing.

4. Commonly Confused Words

Pairs like affect/effect, their/there/they’re, and its/it’s are spelled correctly and pass a basic spell-check, which is exactly what makes them dangerous — the mistake is invisible unless you’re specifically checking word choice, not spelling. Grammarly flags these because it’s checking usage in context, not just whether a word exists in the dictionary.

5. Run-On Sentences and Comma Splices

Non-native writers translating thought patterns from languages with different sentence-boundary conventions often end up joining two complete thoughts with just a comma, or stacking clauses that should be split into separate sentences. It doesn’t change the meaning, but it reads as less polished — and it’s a pattern that’s genuinely hard to hear in your own head while writing, since you already know where you intended the “break” to be.

Why These Are Hard to Catch Yourself

All five of these share the same trait: they don’t interrupt your own reading, because you already know what you meant to say. A reader who doesn’t have that context notices immediately. That gap — between how a sentence sounds to the person who wrote it and how it sounds to everyone else — is exactly what a second pass through a tool like Grammarly is useful for, especially for formal writing like reports and emails where small mistakes are more visible.

FAQ

Does the free plan catch all five of these? Yes — all five fall under core grammar and correctness checks, which are available on Grammarly’s free plan. The paid tiers add more around tone, clarity, and fluency, but these specific error types don’t require an upgrade.

Is this list specific to non-native writers, or does everyone make these mistakes? Native writers make some of these too (subject-verb agreement in long sentences, comma splices, in particular), but articles and prepositions are disproportionately a non-native-writer pattern, since they’re governed more by usage and instinct than by a rule you can consciously apply.

Is there a faster way to catch these without running everything through a tool? Reading your writing out loud helps for some of these (run-ons especially), but articles and prepositions are genuinely hard to self-catch because your brain auto-corrects them while reading your own writing. That’s the specific gap an outside check — human or tool — is useful for.

Final Thoughts

None of these five are the kind of mistakes that make writing hard to understand — they’re the kind that make it read as slightly non-native, which matters more than it should in formal writing like reports and client emails. A free grammar checker is a low-effort way to close that gap on the mechanical side, even if it can’t help with tone, structure, or whether the writing actually makes your point.

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