Common grammar mistakes

A handful of grammar mistakes cause most of the errors in everyday writing. Fix these few and your writing will be noticeably cleaner. You do not need to master every rule.

The mistakes to fix

1. Subject–verb agreement. The subject and verb must agree in number. "The list of items is long" — the subject is "list" (singular), so "is." The error comes from matching the verb to the noun nearest it ("items" is plural). Find the true subject.

2. Sentence fragments. A fragment is a group of words that is not a complete sentence. "Because it rained." Fix by joining it to the sentence it belongs to.

3. Run-ons and comma splices. Two complete sentences joined with no punctuation (run-on) or only a comma (comma splice). "The report was ready, it went to the client." Fix with a period, a semicolon, or a conjunction.

4. Its vs it's. "It's" = "it is"; "its" = possessive. Say "it is" to test.

5. Your vs you're and their/there/they're. "You're" = "you are"; "your" = possessive. "There" = place; "their" = possessive; "they're" = "they are."

6. Its/it's and similar homophones — aloud (out loud) vs allowed (permitted), affect (verb) vs effect (noun), then (time) vs than (comparison), to/too/two, whose/who's.

7. Then vs than. "Than" compares ("better than"); "then" is about time ("back then").

8. Effect vs affect. "Affect" is usually a verb ("to affect"); "effect" is usually a noun ("the effect").

9. Misplaced modifiers. A phrase that modifies the wrong thing. "Walking to the store, the rain fell" suggests the rain was walking. Put the modifier next to what it describes.

10. Redundant double negatives. "I did not go nowhere" → "I did not go anywhere" or "I went nowhere."

How to improve

Read your work aloud — your ear catches many of these. Set your spellchecker to your English variety and turn on grammar checks. Keep a personal list of the errors you repeat and check for them specifically. The proofreading checklist and tools help you catch them before you submit.

Common mistakes gone wrong

Trying to learn every rule and getting overwhelmed. Relying only on a spellchecker (it misses homophones and agreement). Fixing errors but not understanding why, so they come back. Being so afraid of mistakes you never write.

Practical tips

• Fix agreement, fragments and run-ons first — they cause the most confusion.
• Use the "say it as its/its it is" test for the hardest homophones.
• Keep a one-line list of your three most common errors and check for them.

Checklist

• I checked subject–verb agreement.
• No sentence fragments or run-ons or comma splices.
• its/it's, your/you're, their/there/they're are correct.
• then/than and affect/effect are correct.
• No misplaced modifiers.
• No redundant double negatives.