Grammar Tips — 10 Common Mistakes and How to Fix Them

Why Grammar Still Matters in 2026

In an era of casual texting and emoji-filled messages, some argue that grammar rules are outdated. But in professional communication, grammar errors immediately undermine your credibility. A study by Grammarly found that professionals who made fewer grammar errors in their LinkedIn profiles advanced to higher positions and received more promotions. First impressions in writing happen instantly — a misplaced apostrophe or confused homophone can make a well-researched proposal look careless.

This does not mean every text message needs to be perfect. Context matters. But understanding the rules gives you the power to choose when to follow them and when to break them deliberately. Here are 10 grammar mistakes that appear in professional writing far too often, along with clear explanations of how to fix them.

1. Your vs. You’re

Your is possessive — it means belonging to you. Your report is due Friday. You’re is a contraction of you are. The test: if you can replace the word with you are and the sentence still makes sense, use you’re. If not, use your. This mistake appears in roughly 15 percent of professional emails according to editing tools, and it instantly signals carelessness to careful readers.

2. Their, There, and They’re

Their shows possession — their presentation was excellent. There indicates a place or existence — the file is over there or there are three options. They’re contracts they are — they’re arriving at noon. Again, the contraction test works perfectly: if they are fits, use they’re. If you mean possession, use their. Everything else is there.

3. Its vs. It’s

This one trips up even experienced writers because it seems to contradict the apostrophe-for-possession rule. Its without an apostrophe is possessive — the company changed its logo. It’s with an apostrophe is always a contraction of it is or it has. Think of its as being in the same family as his and hers — none of those possessive pronouns use apostrophes.

4. Effect vs. Affect

Affect is usually a verb meaning to influence — the delay will affect our timeline. Effect is usually a noun meaning the result — the effect of the delay was significant. The memory trick: Affect is the Action (both start with A), Effect is the End result (both start with E). There are rare exceptions, but in 95 percent of professional writing, the verb/noun distinction covers it.

5. Who vs. Whom

Who is for subjects — the person doing the action. Whom is for objects — the person receiving the action. Substitute he or him to test: if him sounds right, use whom (both end in M). Who sent the email? (he sent it). To whom should I address this? (address it to him). Use our Grammar Checker at steinketool.com to catch these errors automatically.

6. Fewer vs. Less

Fewer is for countable items — fewer meetings this week. Less is for uncountable quantities — less time wasted in meetings. If you can count the individual items, use fewer. If it is a continuous quantity, use less. Fewer dollars, less money. Fewer employees, less staff. Fewer hours, less time. The supermarket sign 10 items or less is technically wrong — it should be 10 items or fewer.

7. Dangling Modifiers

Walking to the meeting, the presentation slides fell off the table. This sentence implies the slides were walking. The modifier walking to the meeting dangles because the subject it is meant to describe (a person) is missing. Correct: Walking to the meeting, I dropped the presentation slides. Always check that the noun immediately after an introductory phrase is the one performing that action.

8. Comma Splices

A comma splice occurs when you join two independent clauses with just a comma. The deadline is Friday, we need to finish testing today. This is two complete sentences joined incorrectly. Fix it by using a period, a semicolon, or a comma plus a conjunction: The deadline is Friday, so we need to finish testing today. Comma splices are one of the most common mistakes in professional writing and one of the easiest to fix once you learn to recognize them.

9. Subject-Verb Agreement

The team of developers are working on the fix. Despite sounding right to many ears, this is incorrect. The subject is team (singular), not developers. Correct: The team of developers is working on the fix. This gets tricky with collective nouns and phrases where the subject and verb are far apart. The rule: identify the actual subject (ignoring prepositional phrases) and match the verb to it.

10. Misplaced Apostrophes in Plurals

The company hired three developer’s. No. Apostrophes do not make words plural. The company hired three developers is correct. The developer’s code is correct only when showing possession (the code belonging to the developer). This mistake appears on business signs, marketing materials, and professional documents with alarming frequency. Plurals never need apostrophes. Possessives do.