Common Error Patterns & Quick Fixes
Here's the thing — the same handful of slips turn up again and again, in essays and CVs and the email you fire off at 4:55 on a Friday. This is a glance card, not a lesson: the pattern, why it catches people, the quick fix, a before-and-after, and a link straight home to the article that actually teaches it. Scan the left-hand column, fix what you spot, and jump home for anything that still feels shaky. For the full diagnosis of any of these, go to P10 · Common Errors & Usage Problems — the clinic this page condenses.
| Pattern | Why it trips people up | Quick fix | Before → After | Link home |
|---|---|---|---|---|
| its / it's | It is already a pronoun, so the apostrophe feels like it should mark possession. | If you mean it is or it has, write it's; for possession, its. | The dog wagged it's tail. → The dog wagged its tail. | P2 · Possessive apostrophes & its/it's |
| your / you're | Homophones — the ear can't tell them apart. | You're = you are; your = belonging to you. | Your welcome anytime. → You're welcome anytime. | P2 · Pronouns & contractions · P8 · Confusables |
| their / there / they're | Three little words, one sound; fingers go on autopilot. | They're = they are; their = belonging; there = place. | Their going to miss the train if they stay their. → They're going to miss the train if they stay there. | P8 · Confusables · P2 · Pronouns |
| who's / whose | Same sound trap as its/it's. | Who's = who is/has; whose = belonging. | Whose going to collect the keys? → Who's going to collect the keys? | P2 · Pronouns & possessives |
| affect / effect | Near-identical vowels; both live near the same idea. | Usually: affect = verb (to influence); effect = noun (the result). | The rule will effect everyone. → The rule will affect everyone. | P8 · Confusables |
| then / than | Typing speed and speech rhythm blur them. | Than for comparison; then for time or sequence. | She is taller then me. → She is taller than me. | P8 · Confusables |
| to / too / two | Three common words sharing one sound. | To = direction/infinitive; too = also/excessively; two = 2. | I want too go to. → I want to go too. | P8 · Confusables |
| fewer / less | In speech, less covers everything, and it bleeds into writing. | Fewer with things you can count; less with mass/quantity. | There were less desks than last year. → There were fewer desks than last year. | P8 · Confusables |
| Subject–verb agreement | A long phrase sits between subject and verb, and the verb copies the nearest noun. | Find the real subject and match the verb to it. | The box of pencils are under the desk. → The box of pencils is under the desk. | P5 · Subject–verb agreement |
| Pronoun–antecedent slips | The pronoun and its noun disagree in number, or the noun is too far away. | Match number and person; keep the pronoun near a clear noun. | Each girl brought their pencil. → Each girl brought her pencil. (or) The girls brought their pencils. | P5 · Pronoun–antecedent agreement & singular they |
| Comma splice | Two complete sentences joined with only a comma — it feels like a pause, but it's too weak to hold. | Use a full stop [US: period], a semicolon, or a comma + conjunction. | I finished early, the café was still open. → I finished early. The café was still open. (or) …early, and the café… | P3 · Run-ons · P6 · Commas |
| Run-on (fused sentence) | Two clauses jammed together with no punctuation at all. | Separate them, or join with a semicolon or conjunction. | The deadline passed we still submitted. → The deadline passed, but we still submitted. | P3 · Run-ons & fragments |
| Sentence fragment | A dependent clause is left standing alone as if it were a whole sentence. | Attach it to a main clause, or make it independent. | Because it was raining. → Because it was raining, we stayed in. | P3 · Fragments |
| Misplaced / dangling modifier | The describing phrase sits next to the wrong noun — or floats free with no subject at all. | Park the modifier next to what it describes, or recast the sentence. | Walking into the room, the projector caught my eye. → Walking into the room, I noticed the projector. | P3 · Modifiers & word order |
| Apostrophe in a plain plural | The "add 's" rule for possession leaks into ordinary plurals. | Plurals take only -s/-es; apostrophes are for possession or missing letters. | CD's for sale. / The Smith's are here. → CDs for sale. / The Smiths are here. | P2 · Possessive apostrophes · P6 · Apostrophes |
| me / I (case mix-up) | Hypercorrection — "you and I" gets over-applied into object slots. | After a preposition or as an object, use me, him, her, us, them. | Between you and I, the plan is risky. → Between you and me, the plan is risky. | P2 · Pronouns |
| could of / should of | Could've sounds exactly like could of. | It's always have: could have / could've — never of. | I could of finished earlier. → I could have finished earlier. | P4 · Modals & perfect forms · P8 · Confusables |
| Tense shifts | Mid-story, we slip from past to present without noticing. | Pick a main tense and hold it unless the time genuinely changes. | I walked into the room and everyone is staring. → I walked into the room and everyone was staring. | P4 · Tenses & aspect |
| that / which | Defining and commenting clauses blur together. | Defining clause: no commas; extra-information which: commas around it. | The book, that I borrowed, is overdue. → The book that I borrowed is overdue. | P3 · Clauses · P6 · Commas |
Where UK and US genuinely differ
Most of these patterns behave the same on both sides of the Atlantic. A few are dialect-driven — where a "mistake" in one variety is simply the house rule in the other. Only the honest ones are below; a blank beats an invented split.
| Pattern | UK | US | Status |
|---|---|---|---|
| Collective-noun agreement (team, government, staff) | Often plural: the team are playing. | Almost always singular: the team is playing. | tendency — see P5 |
| Full stop/comma with closing quotation marks | Often placed outside the quotes when not part of the quoted words | Almost always placed inside the closing quotation mark | tendency — see P6 · Quotation marks |
Everything else on the card above is shared. Spelling and vocabulary differences (-ise/-ize, towards/toward, and the like) aren't errors at all — pick your variety and keep it steady. See P8 · UK/US spelling & vocabulary.
Common Mistake: Treating the homophone rows (its/it's, your/you're, their/there/they're) as trivial. They look harmless until a job application or a closed-book exam puts them under a spotlight. One read-aloud after drafting catches most of them.
Pro-Tip: For subject–verb and pronoun problems, mentally cross out the phrase between the subject and the verb — the box ~~of pencils~~ is — and the right form usually jumps out.
Common Mistake: Fixing only the easy ones (apostrophes, homophones) while a dangling modifier or a remote subject–verb mismatch sails past. The card is deliberately mixed for that reason.
Pro-Tip: If the same error turns up twice in one document, don't patch it in isolation — open the linked article. The pattern only stops recurring once the "why" clicks. Drills live in P12 · 17 Practice Sets.
Where each pattern is taught
- P2 Parts of Speech — pronouns, possessives, apostrophes, its/it's
- P3 Sentence Structure & Syntax — clauses, fragments, run-ons/comma splices, modifiers
- P4 The Verb System — tenses, aspect, modals and the perfect forms behind could of
- P5 Agreement & Concord — subject–verb, pronoun–antecedent, singular they
- P6 Punctuation — commas, apostrophes, quotation marks
- P8 Spelling, Morphology & Word Choice — confusables, UK/US spelling and vocabulary
- P9 Style, Formality & Register — when "correctness" tightens or relaxes
- P10 Common Errors & Usage Problems — the full clinic this page condenses
- P12 · 17 Practice Sets — drills built on these exact patterns
That's the whole card. Nobody's born knowing this lot — you just need somewhere to look.