Introduction
In today’s professional world, writing is everything. Whether it’s an email to a client, a report for your manager, or a LinkedIn post showcasing your expertise, your words represent you. One careless grammar mistake can make you appear careless, unprofessional, or even uneducated — no matter how brilliant your ideas are.
The good news? These mistakes are easy to fix once you know what to look for. In this post, we’ll cover the five most common grammar errors professionals make, with clear examples and tips to avoid them. Master these, and you’ll instantly look more polished and confident in your writing.
1. Misused Apostrophes
Apostrophes are small, but their misuse can make your writing look sloppy. They’re meant for showing possession (John’s book) or forming contractions (don’t, it’s), not for making words plural.
Common Mistakes:
❌ “Our company value’s integrity.”
❌ “We’re hiring 5 developer’s.”
Corrected Versions:
✅ “Our company values integrity.”
✅ “We’re hiring 5 developers.”
Pro Tip: If you can remove the apostrophe and the sentence still makes sense, it was likely wrong. For plurals, just add an ‘s’.
2. Subject–Verb Agreement Errors
One of the most overlooked mistakes in professional writing is a mismatch between the subject and verb. If the subject is singular, the verb must be singular. If the subject is plural, the verb must be plural.
Common Mistakes:
❌ “The results of the study shows clear trends.”
❌ “The team are working on the project.”
Correct Versions:
✅ “The results of the study show clear trends.”
✅ “The team is working on the project.”
Pro Tip: Focus on the main subject of the sentence, not words in between.
3. Comma Overload (or Underuse)
Commas can change the meaning of a sentence — sometimes dramatically! Overusing commas makes sentences clunky; underusing them can create confusion.
Funny Example:
❌ “Let’s eat John.”
✅ “Let’s eat, John.”
Professional Example:
❌ “After reviewing the report I think we should make changes.”
✅ “After reviewing the report, I think we should make changes.”
Pro Tip: If you can pause naturally when reading aloud, that’s usually where a comma belongs.
4. Confusing Common Words
Even seasoned professionals mix up similar words, especially under pressure. Small mistakes distract from your message and make you appear careless.
Common Mix-ups:
affect vs. effect
then vs. than
their vs. there vs. they’re
Example (affect vs. effect):
❌ “The changes effected the entire team.”
✅ “The changes affected the entire team.”
Then vs. Than
Then = relates to time or what happens next.
Than = used for comparisons.
Examples:
“First we’ll review the report, then we’ll meet with the client.”
“She’s taller than her brother.”
“Back then, the company had only five employees.”
“I’d rather email the proposal than call about it.”
Pro Tip: If you can replace the word with “next” or “at that time”, it should be then. If it’s a comparison, use than.
Pro Tip: Make a small cheat sheet of the words you frequently confuse — it saves embarrassment and builds confidence.
Their vs. There vs. They’re
Their = shows possession (belongs to them).
There = refers to a place or is used as a pronoun (“there is/there are”).
They’re = contraction of they are.
Examples:
“The managers shared their notes after the meeting.” (possession)
“Let’s meet over there near the conference room.” (place)
“They’re working late to finish the project.” (they are)
Trick to Remember:
Their → heir (something you own).
There → has here inside (place).
They’re → replace with they are to check.
5. Run-On Sentences
Long, rambling sentences make your writing hard to read. They also reduce clarity and weaken your authority.
Common Mistake:
❌ “I wanted to follow up with you I think the report looks good we just need a few edits.”
Correct Version:
✅ “I wanted to follow up with you. I think the report looks good — we just need a few edits.”
Pro Tip: Break ideas into shorter sentences. Use punctuation like periods, dashes, or semicolons to add structure.
Conclusion: Small Fixes, Big Impact
Correcting these five mistakes can instantly elevate your professional writing, but they’re just the tip of the iceberg. There are 10 critical grammar fixes that every professional should master to write confidently and clearly. Keep your eyes peeled for these, in the next post.