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Grammar Basics · Topic V

Common Errors in English: A Complete Guide

Their, there, and they're. Affect and effect. Fewer and less. Here are the mistakes that trip up even confident writers — and exactly how to fix them for good.

EDUSAMBAM Editorial Team | 20 min read | Last updated: October 2026 | Grammar
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Most English mistakes are not random. A small group of confusing words and rules cause a large share of the errors that even careful writers make. Learn this group once, and your writing becomes cleaner almost overnight.

This guide gathers the most common errors in one place and shows how to fix each one. It covers words that sound alike, pronoun and agreement problems, fewer and less, sentence-level errors such as comma splices and dangling modifiers, apostrophes and spelling, and the "rules" that turn out to be myths. It also shows you how to build a personal error list and a three-pass proofreading routine, with two worked examples, a checklist and ten practice questions.

It builds on Parts of Speech, Sentence Structure, Punctuation Rules and Tenses & Verb Forms. Spelling in this guide follows British English.

1.Why the Same Errors Keep Appearing

Errors repeat for four main reasons:

It also helps to separate errors from choices. An error breaks a convention that careful readers expect in standard written English (for example, could of). A choice is a matter of style or formality (for example, using less in everyday speech where formal writing prefers fewer). This guide marks the difference, because you need to fix the first kind and may only need to think about the second.

2.Words That Sound Alike (or Nearly Alike)

These pairs and groups cause the most trouble. Read each row slowly, then use the memory tip.

The swap test for their / there / they're
Try the tests in this order.
A three-step test for their, there and they'reStep one: can you say they are? Then write they're. Step two: does it show belonging, as in their bags? Then write their. Step three: if it is a place or the start of an existence sentence, write there. 1Can you say "they are" here?They are late = They're latethey're 2Does it show belonging?their bags, their idea (like my, our)their 3Place, or "there is / there are"?over there, there is a problemthere

Diagram 1. The same method works for your / you're (try "you are") and its / it's (try "it is").

WordsMeaning and exampleMemory tip
their / there / they'reBelonging: their bags. Place or existence: over there; there is a problem. They are: they're late.Use the swap test above.
your / you'reYour book (belonging). You're ready (you are).Say "you are" aloud. If it fits, use you're.
its / it'sThe dog wagged its tail (belonging). It's late (it is / it has).Only the contraction has an apostrophe.
whose / who'sWhose pen is this? (belonging). Who's coming? (who is / who has).Try "who is".
to / too / twoto the shop; too = also or excessively (too hot); two = the number 2.Too has too many o's: it means "more".
then / thanFirst…, then… (time). Taller than me (comparison).Then = time; than = comparison.
loose / loseA loose button (not tight). To lose a game (to fail to keep).Lose has lost an o.
accept / exceptI accept your offer (receive). Everyone except me (not including).Except = excluded; both start with ex.
affect / effectRain will affect the match (verb: to influence). The effect was serious (noun: a result).Affect = Action; Effect = End result.
principal / principleThe principal of the school; the principal reason (main). A moral principle (a rule or belief).The principal is your pal.
weather / whetherRainy weather; I wonder whether it will rain (if).Whether asks a question, as wh- words do. Weather is what you see in the sky.
quiet / quiteA quiet room; quite good (fairly).Quiet has two syllables (qui-et); quite has one.
stationary / stationeryA stationary car (not moving); stationery (paper, pens).Stationery has an e like envelope.
advice / adviseGood advice (noun). I advise you (verb).Noun has c (ice); verb has s.
practice / practiseBritish English: practice is the noun, practise is the verb. American English normally uses practice for both.Same pattern as advice/advise. Choose one system and stay with it.
licence / licenseBritish English: licence (noun), license (verb). American English uses license for both.Same pattern again.

Other everyday slips. Write should have, could have and would have, never "should of": we say them as should've, which sounds like should of. Write a lot as two words (never "alot"). Write every day as two words for "each day" and everyday as one word for "ordinary" (everyday clothes). Write maybe for "perhaps" and may be for "might be" (It may be late).

3.Pronoun Problems: I / Me, Who / Whom, Myself

I or me? The confusion happens mostly with two people. Remove the other person and test each pronoun alone.

IncorrectCorrectTest
Me and John went to the store.John and I went to the store."I went", not "me went"
She gave it to John and I.She gave it to John and me."gave it to me", not "to I"
Between you and I, it is late.Between you and me, it is late.After a preposition, use me

Who or whom? Use who when the answer would be he, she, they. Use whom when it would be him, her, them. Who called you? (He called.) To whom should I write? (Write to him.) In everyday speech, who is common even where whom is traditional, but formal writing and exams usually expect whom after a preposition.

Myself. Myself is for when you are doing something to yourself (I taught myself to type) or for emphasis (I did it myself). It is not a fancier word for I or me. Write Please contact Sara or me, not "Sara or myself".

Pronoun agreement. A pronoun should match the word it refers to. Write Students should bring their books, not "Students should bring his book". For a single person of unknown gender, many style guides now accept the singular they (Everyone brought their own lunch). Check which form your exam board or school prefers.

4.Subject-Verb Agreement

A singular subject takes a singular verb, and a plural subject takes a plural verb. Errors usually come when other words stand between the subject and the verb.

Find the real subject
Ignore the phrase in the middle.
Finding the real subject of a sentenceIn the sentence The list of items is on the table, the phrase of items is greyed out. The real subject is list, which is singular, so the verb is. Thelistof itemsison the table. ignore this phrase list (one thing) → is 1. Cross out the phrase between subject and verb. 2. Decide: is the real subject one thing or several? 3. Match the verb to it.

Diagram 2. "The list … is" (not "are"). The nearby word items does not change the subject.

5.Fewer or Less, Many or Much, Number or Amount

The basic rule is simple. Use fewer with things you can count one by one, and less with things you cannot: fewer people, fewer chairs, fewer mistakes; less water, less time, less information. In the same way, use many and number of with countable nouns (many books, a large number of students), and much and amount of with uncountable nouns (much rice, a small amount of money).

Three details make the picture accurate:

6.Sentence-Level Errors

Fragments, run-ons and comma splices

A fragment is an incomplete sentence (Because it was raining.). A run-on joins two complete sentences with nothing at all (It was raining we stayed inside.). A comma splice joins them with only a comma (It was raining, we stayed inside.). There are four standard ways to repair a comma splice or run-on:

FixExample
Full stopIt was raining. We stayed inside.
SemicolonIt was raining; we stayed inside.
Comma and a conjunctionIt was raining, so we stayed inside.
Make one part dependentBecause it was raining, we stayed inside.

Dangling and misplaced modifiers

A modifier must sit next to the word it describes. A dangling modifier has nothing sensible to describe: Walking to the store, the rain started. (The rain was not walking.) Fix it by naming the doer: Walking to the store, I got caught in the rain. A misplaced modifier is in the wrong place: I only ate the cake (and did nothing else with it) versus I ate only the cake (nothing else). Put only, almost and nearly directly before the word they limit.

Faulty parallelism

Items in a list should have the same form. Write She likes swimming, running and cycling, not "She likes swimming, to run and cycling".

Tense shifts

Do not switch tenses without a reason. Write He opened the door and saw a letter, not "He opened the door and sees a letter".

Double negatives

Standard English uses one negative for one idea: I don't know anything or I know nothing, not "I don't know nothing". Many dialects and other languages do use two negatives for emphasis, but standard written English does not. Do not confuse this with a deliberate pair such as not unhappy, which is a style choice meaning "fairly content".

7.Apostrophes and Spelling Traps

Plurals do not need apostrophes. Write apples and bananas, the 1990s, two CDs. A few rare exceptions exist, such as lower-case letters (mind your p's and q's), but in everyday writing, treat an apostrophe before a plural s as an error.

Possession. Add 's to a singular noun (the boy's bag) and only an apostrophe to a regular plural ending in s (the boys' bags). Irregular plurals take 's (the children's room).

Common misspellings and tips:

WordTrapTip
definitely"definately"It has "finite" inside it.
separate"seperate"There is "a rat" in sep-a-rat-e.
necessary"neccessary"One collar (c), two sleeves (ss).
accommodate"acommodate"Two c's and two m's.
receive / believeie or ei?"i before e, except after c", but note exceptions such as weird and science.
occurred"occured"Double the r before -ed.
February, library"Febuary", "libary"Say each syllable slowly: Feb-ru-ary, li-brar-y.

British spelling uses colour, favourite, centre, organise, travelling. American spelling uses color, favorite, center, organize, traveling. Both are correct in their own system. The important rule is to choose one and use it consistently. Match the spelling your school, exam board or reader expects.

8.Why Spell-Check Is Not Enough

A spell-checker looks for words that do not exist. It cannot tell you that a real word is in the wrong place. This sentence passes most spell-checks: "Their going to loose the match, but there coach is quiet happy." Every word is a real word, yet there are four errors. Grammar checkers help, but they sometimes suggest wrong changes, so treat their advice as a prompt to think, not an order. The only dependable method is a careful human read, aloud if possible.

9."Rules" That Are Really Myths

Some rules taught in school are not errors at all. Usage guides and dictionary publishers say these are acceptable in standard English:

Your teacher may still prefer to avoid them in exams, and that is a reasonable style preference to follow. But do not "correct" them as if they were errors in other people's writing.

10.How to Stop Repeating the Same Errors

Do not try to memorise every rule. Instead, find your own five most common errors and fix them one at a time.

  1. Collect. Look at corrected work, teacher comments and old drafts. Write down each error and the correct form.
  2. Rank. Choose the five that appear most often.
  3. Practise. Write three new sentences for each, using the correct form.
  4. Test. After a week, check whether the errors have gone from your new writing.
  5. Replace. When one is fixed, move the next error up your list.
Three proofreading passes
One job per pass keeps your attention focused.
Three proofreading passesThree bars: first read for meaning, second check grammar and agreement, third hunt for your own personal error list. PASS 1Read for meaning and clarity PASS 2Check sentences, agreement, punctuation PASS 3Hunt your personal error list

Diagram 3. Reading aloud helps in every pass.

11.Worked Examples

Example A: Proofreading a paragraph

Find and correct the errors in this paragraph. There are twelve.

Their are fewer students in our class this year, and the teacher is more strict then last year. Me and my friend Sara goes to the library everyday, where we practice our speaking. Walking home, the rain started and we got soaked. The principle asked who we thought should be the monitor, and he didn't give us no time to decide. Its a shame that alot of students dont use there time wisely.

#ErrorCorrection and reason
1Their areThere are (existence)
2more strict thenstricter than (comparison)
3Me and my friend Sara goesMy friend Sara and I go (pronoun and agreement)
4everydayevery day (each day)
5practice (verb)practise (British verb)
6Walking home, the rain startedAs we walked home, it started to rain (dangling modifier)
7principleprincipal (head of school)
8didn't give us no timegave us no time (double negative)
9Its a shameIt's a shame (it is)
10alota lot
11dontdon't (missing apostrophe)
12there timetheir time (belonging)

Corrected paragraph. There are fewer students in our class this year, and the teacher is stricter than last year. My friend Sara and I go to the library every day, where we practise our speaking. As we walked home, it started to rain and we got soaked. The principal asked who we thought should be the monitor, and he gave us no time to decide. It's a shame that a lot of students don't use their time wisely.

Note two things. "Fewer students" and "who we thought should be" were already correct, so good proofreading also means not changing what is right.

Example B: Fixing a comma splice four ways

The splice: The library was closed, we studied at home.

1Spot it. Two complete sentences joined by only a comma.
2Choose a repair. Full stop: The library was closed. We studied at home.
3Or: semicolon, The library was closed; we studied at home.
4Or: conjunction, The library was closed, so we studied at home.
5Or: dependent clause, Because the library was closed, we studied at home.

Try it yourself. Correct this sentence: "There are less students here then last year, the library is quiet."

Sample answer: "There are fewer students here than last year, so the library is quiet." Four errors were fixed: there (existence), fewer (countable), than (comparison), and the comma splice.

12.Your Proofreading Checklist

For more on editing, see Editing Your Own Work.

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13.Common Mistakes When Fixing Errors

MistakeBetter habit
Trusting spell-check completelyRead it yourself, aloud
Fixing everything in one passUse separate passes for meaning, grammar and your error list
Memorising rules without examplesLearn each rule with a sentence of your own
Over-correcting ("between you and I", "whom" in the wrong place)Use the test for each pronoun; do not guess
Changing correct textFix only what you can explain
Mixing British and American spellingChoose one system and keep it
Proofreading straight after writingLeave it for an hour or a day first

14.Common Myths About Errors

MythYou must never end a sentence with a preposition.
FactDictionary publishers and usage guides accept it; it often sounds more natural.
MythYou must never split an infinitive.
FactIt is acceptable, particularly with one short word, when it sounds natural.
Myth"Less" is always wrong with countable things.
FactIt is traditional to use fewer in careful writing, but less is common in speech and is normal with time, money and distance (less than five pounds).
MythGood writers do not make these mistakes.
FactAll writers slip. Good writers proofread and know their own weak spots.

15.Key Terms

Homophone: a word that sounds the same as another but has a different meaning or spelling.
Contraction: a shortened form with an apostrophe, such as they're or it's.
Subject-verb agreement: matching the verb to a singular or plural subject.
Countable noun: a noun you can count one by one (chairs, ideas).
Uncountable noun: a noun not counted separately (water, advice).
Fragment: an incomplete sentence.
Run-on / comma splice: two complete sentences joined with no punctuation or only a comma.
Dangling modifier: a describing phrase with nothing sensible to describe.
Parallelism: using the same form for items in a list.
Double negative: two negatives for one idea, avoided in standard English.
Proofreading: checking a finished text for errors.

16.Why This Matters

Small errors change how readers judge your ideas. A single "their" for "there" will not ruin an essay, but a page full of such slips makes a good argument look careless, and in exams, errors can cost marks. The reassuring fact is that a small group of errors causes most of the damage, so a short personal list and a calm proofreading routine can raise the quality of all your writing. Continue with Editing Your Own Work and Formal vs. Informal English.

Key points to remember
For teachers and parents

Activity: give students a paragraph with ten planted errors and ask them to find them in pairs, naming the rule for each. Then have each student create a personal error list from their last two essays.

Please note: this guide uses British spelling (practise, licence) and a traditional position on forms such as neither is and fewer, because these are usually expected in school writing. Usage varies between countries and styles, so students should follow the guidance of their own syllabus and teacher.

Where These Facts Come From
Further Reading
Test Your Understanding

Practice Questions

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1.Which sentence is correct?
2.The long delay had a serious ___ on the project.
3.There are ___ students in the library today than yesterday.
4.Which sentence is correct?
5.The list of names ___ on the board.
6.Which sentence has a dangling modifier?
7.Which sentence is a comma splice?
8.Which sentence is correct in British English?
9.Why is a spell-checker not enough for proofreading?
10.Which statement about grammar "rules" is most accurate?
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