The grammar mistakes that damage writing the most are rarely the dramatic ones. They are the small, repeated slips that a reader notices without quite being able to name — and each one chips away slightly at how credible your writing feels.
You do not need to memorize a grammar textbook to write well. You need to recognize a short list of recurring errors, understand why they happen, and know how to catch them before they reach a reader. Here are seven of the most common ones, along with the fix for each.
1Subject-verb agreement across long sentences
The longer the distance between a subject and its verb, the easier it is to lose track of which one governs the sentence. “The list of requirements, along with the supporting documents, are due Friday” is wrong — the subject is “list,” singular, so the verb should be “is.” Long modifying phrases between subject and verb are the most common trigger for this mistake.
2Misplaced modifiers
A modifier should sit next to the word it describes. “Running late, the meeting started without her” accidentally implies the meeting was running late, not her. The fix is to move the modifier next to the person or thing it actually describes: “Running late, she missed the start of the meeting.”
3Comma splices
A comma splice joins two complete sentences with only a comma: “The report was late, the client was unhappy.” This needs a period, a semicolon, or a coordinating conjunction like “and” or “but” to properly connect the two independent thoughts.
4Its versus it’s
“It’s” is always a contraction for “it is” or “it has.” “Its” is always possessive. This is one of the most common typing errors precisely because most possessives use an apostrophe, which makes “its” feel like an exception worth double-checking every time.
A reliable test
Replace the word with “it is” in the sentence. If it still makes sense, use “it’s.” If not, use “its.”
5Dangling modifiers
A dangling modifier describes something that is not actually present in the sentence. “After finishing the report, the printer broke” implies the printer finished the report. The intended subject — the person who finished the report — needs to actually appear in the sentence.
6Confusing “who” and “whom”
“Who” is used for the subject of a clause; “whom” is used for the object. A quick trick: if you can replace the word with “he” or “she,” use “who.” If you can replace it with “him” or “her,” use “whom.” Most casual writing has shifted toward using “who” almost everywhere, but knowing the distinction still matters in formal writing.
7Inconsistent verb tense within a paragraph
Shifting between past and present tense without a clear reason confuses the reader about when events are happening. “She opened the document and reviews the changes” mixes past and present tense in the same sentence. Pick a tense for a given passage and stay consistent unless the timeline genuinely shifts.
Why these mistakes are worth fixing
None of these errors are catastrophic on their own. But readers process grammar unconsciously, and a pattern of small mistakes signals carelessness even when the underlying ideas are strong. Fixing them is less about following rules for their own sake and more about making sure nothing distracts from what you are actually trying to say.
Grammar mistakes are rarely a sign that someone does not know the rules — they are usually a sign of writing quickly and editing lightly. The seven patterns above account for a large share of the errors that slip through in everyday writing, which makes them worth specifically checking for during your next editing pass.
Bookmark this list, or better yet, run your next draft past a tool that catches these patterns automatically. Either way, the goal is the same: let your ideas be the thing readers remember, not the small errors surrounding them.
Catch grammar slips and awkward phrasing before you publish.
Try SentenceRewriter.co free
