A manual checklist for finding and fixing 14 frequent grammar errors in essays. Read this before you submit your work.
The errors below rank high in student writing. Each row shows a wrong example, a correct version, and the rule. Use this table as you edit.
| Mistake | Wrong | Right | Why |
|---|---|---|---|
| its vs. it's | The dog ate it's food. | The dog ate its food. | it's = "it is"; its = possessive. Use its when showing what something owns. |
| their vs. there vs. they're | There going to their house over there. | They're going to their house over there. | they're = "they are"; their = possessive; there = place or "there is". |
| your vs. you're | Your going to submit you're paper. | You're going to submit your paper. | you're = "you are"; your = possessive. Replace with "you are" to test. |
| then vs. than | This essay is longer then the first one. | This essay is longer than the first one. | than is for comparison; then is for time or sequence. "Than" has an 'a' like "cAke" (for comparison). |
| affect vs. effect | The rain will effect our study time. | The rain will affect our study time. | affect (verb) = to influence; effect (noun) = the result. "Affect" is usually the verb you want. |
| who vs. whom | The professor who I asked was helpful. | The professor whom I asked was helpful. | who is the subject (he/she); whom is the object (him/her). Replace with "him" to test — if it fits, use whom. |
| less vs. fewer | There are less mistakes in this draft. | There are fewer mistakes in this draft. | fewer for things you can count; less for amounts or mass. You count mistakes, so use fewer. |
| lay vs. lie | I'm going to lay down for a nap. | I'm going to lie down for a nap. | lie (no object) = to recline; lay (object required) = to place. "Lie" on the bed; "lay" the book on the table. |
| could of (vs. could have) | I could of finished earlier. | I could have finished earlier. | could have is correct. "Could of" is a mishearing of the contraction "could've" in speech. Never write "of" after modals. |
| comma splice | The essay was good, it had strong examples. | The essay was good; it had strong examples. Or: The essay was good. It had strong examples. | Two independent clauses joined by a comma alone = comma splice. Use a semicolon, period, or add a conjunction (and, but, or). |
| sentence fragment | The study was thorough. Because it included interviews. | The study was thorough because it included interviews. | A fragment is an incomplete sentence. A clause starting with "because" cannot stand alone — attach it to a complete sentence. |
| dangling modifier | After reading the article, the main idea was clear. | After reading the article, I understood the main idea. | A modifier must refer to the nearest noun. "After reading" should modify the subject (you/I), not "main idea". Name who read. |
| subject-verb agreement (collective/indefinite pronouns) | The team are going to win. Or: Everyone are invited. | The team is going to win. Or: Everyone is invited. | Collective nouns (team, group, class) and indefinite pronouns (everyone, anybody, each) take singular verbs in academic American English. |
| misused apostrophes in plurals | The 1990's were a great decade. Two apple's per person. | The 1990s were a great decade. Two apples per person. | Do not use apostrophes to make plurals. Use apostrophes only for possessives (cat's toy) or contractions (it's = it is). |
| i.e. vs. e.g. | Many subjects, e.g. math, science, and history, are required. | Many subjects, i.e. math, science, and history, are required. | i.e. = "that is" (introduces a restatement); e.g. = "for example" (introduces examples). Use i.e. for a complete list that defines something. |
This checklist works best with these companion tools:
Check your essay length, reading time, and sentence statistics to meet assignment requirements.
Fix inconsistent capitalization in titles, headings, and proper nouns across your essay.
Double-check your citation format and reference list before final submission.
Comma splices and its/it's confusion rank among the highest. Many students join two complete sentences with a comma alone or misuse possessive and contraction forms of "it". Both are easily caught by reading your work aloud and checking each sentence carefully.
it's = "it is" or "it has" (contraction). its = possessive form, showing what something owns. Replace it's with "it is" to test: if the sentence still makes sense, use the apostrophe. Otherwise, drop it. Example: "It's a sunny day" (it is a sunny day ✓) but "The cat licked its paws" (the cat licked it is paws ✗, so use its).
No. "Could of" is never correct in writing. It is a common mishearing of the spoken contraction "could've" (could have). In speech, people often pronounce "could've" as "could of", but this is not standard. Always write could have, would have, or should have — never the "of" form. The same applies to might have, may have, and must have.
A comma splice is two independent clauses (complete sentences) joined by only a comma. "The paper was late, the professor accepted it anyway." To fix it, use a semicolon (The paper was late; the professor accepted it anyway.), a period (The paper was late. The professor accepted it anyway.), or add a coordinating conjunction like and, but, or, or yet (The paper was late, but the professor accepted it anyway.).
No. This page is a reference guide and manual proofreading checklist. It does not scan or analyze your writing automatically. Use it as a tool to educate yourself: read each rule, understand the examples, then review your own work by hand. Read your essay aloud, print it out if you can, and check each item in the table one by one. That manual process is how you build better writing habits.