When do I use a semicolon vs. a comma?

Use a semicolon to join two closely related independent clauses without a conjunction: 'It was raining; we stayed inside.' Use a comma before a conjunction (and, but, or, so) to join independent clauses: 'It was raining, so we stayed inside.' Never use a comma alone between independent clauses — that's a comma splice.

What is the Oxford comma and should I use it?

The Oxford comma is the final comma before 'and' in a list: 'red, white, and blue.' It prevents ambiguity — without it, 'I love my parents, Batman and Wonder Woman' suggests your parents are superheroes. Most style guides (APA, Chicago, Oxford) recommend it. AP style omits it unless needed for clarity. Pick one style and be consistent.

What is the difference between affect and effect?

Affect is usually a verb meaning 'to influence': 'The weather affects my mood.' Effect is usually a noun meaning 'a result': 'The effect was immediate.' Memory trick: Affect = Action (both start with A), Effect = End result (both start with E). Rare exceptions: 'effect' as a verb means 'to bring about' ('effect change'), and 'affect' as a noun is a psychology term for emotion.

When do I use who vs. whom?

Who is a subject (does the action): 'Who called?' Whom is an object (receives the action): 'Whom did you call?' Quick test: replace with he/him. If 'he' works, use 'who.' If 'him' works, use 'whom.' Example: 'Who/Whom did you invite?' → 'You invited him' → 'Whom did you invite?'

Where does the period go with quotation marks?

In American English, periods and commas always go inside quotation marks: She said 'hello.' In British English, they go outside unless they're part of the quoted material. For question marks and exclamation points, placement depends on whether the punctuation belongs to the quote or the surrounding sentence.

Grammar & Punctuation Guide: Common Mistakes and How to Fix Them

Writing 11 min read April 2026

Good grammar isn't about being pedantic — it's about being understood. Punctuation errors and grammar mistakes create ambiguity, undermine credibility, and slow readers down. This guide covers the most common mistakes writers make and how to fix them.

Comma Rules That Actually Matter

1. Before Coordinating Conjunctions (FANBOYS)

Use a comma before for, and, nor, but, or, yet, so when joining two independent clauses:

✅ The deadline passed, but nobody noticed.
❌ The deadline passed but nobody noticed. (missing comma)
✅ She wrote code and tested it. (no comma — "tested it" isn't an independent clause)

2. After Introductory Elements

✅ After the meeting, we grabbed lunch.
✅ However, the results were inconclusive.
✅ Running late, she skipped breakfast.

3. The Oxford Comma

With: I thanked my parents, Oprah, and God. (three separate entities)
Without: I thanked my parents, Oprah and God. (could imply your parents are Oprah and God)

4. Comma Splices (The #1 Mistake)

A comma splice joins two independent clauses with just a comma:

❌ It was raining, we stayed inside.
✅ It was raining, so we stayed inside. (add conjunction)
✅ It was raining; we stayed inside. (use semicolon)
✅ It was raining. We stayed inside. (separate sentences)

Semicolons and Colons

Mark	Rule	Example
;	Joins related independent clauses	She finished the report; he reviewed it.
;	Separates complex list items	London, UK; Paris, France; Tokyo, Japan
:	Introduces a list, explanation, or quote	You need three things: focus, patience, and coffee.
:	Follows an independent clause only	❌ The ingredients are: flour, sugar, eggs.

Apostrophe Rules

Possession: the dog's bone (singular), the dogs' bones (plural)
Contractions: it's = it is/it has; don't = do not
its vs. it's: its = possessive (no apostrophe, like his/her); it's = it is
Never for plurals: ❌ apple's for sale → ✅ apples for sale

Commonly Confused Words

Pair	Meanings	Memory Trick
affect / effect	Affect = verb (influence); Effect = noun (result)	A for Action, E for End result
then / than	Then = time; Than = comparison	thAn = compArison
their / there / they're	Possession / place / they are	they're = they are (always expand to check)
your / you're	Possession / you are	you're = you are (expand to check)
who / whom	Subject / object	he → who; him → whom (both end in m)
which / that	Non-essential / essential clause	"which" has commas; "that" doesn't
fewer / less	Countable / uncountable	fewer items, less water
farther / further	Physical distance / figurative extent	farther has "far" (distance)

Subject-Verb Agreement Traps

❌ The list of items are ready. → ✅ The list... is ready. (subject is "list")
❌ Neither the cat nor the dogs is outside. → ✅ ...the dogs are outside. (verb matches nearest subject)
❌ Everyone have their opinion. → ✅ Everyone has their opinion.

Dangling Modifiers

❌ Running to the bus, my coffee spilled. (the coffee wasn't running)
✅ Running to the bus, I spilled my coffee.
❌ After reviewing the data, the report was updated. (who reviewed?)
✅ After reviewing the data, we updated the report.

💡 Tip: Read your writing aloud. If you pause naturally, there's probably a comma. If something sounds awkward, it likely needs restructuring. Use our TextKit tools to check word count, readability, and more.

Frequently Asked Questions

Semicolons join two related independent clauses without a conjunction. Commas go before conjunctions (and, but, so) to join clauses. Never use a comma alone between independent clauses — that's a comma splice.

Most style guides recommend it (APA, Chicago, Oxford). AP style omits it unless needed for clarity. It prevents ambiguity in lists. Pick one style and be consistent.

Affect is usually a verb (to influence). Effect is usually a noun (a result). Memory trick: Affect = Action, Effect = End result.

Who is a subject (does the action), whom is an object (receives it). Quick test: if "him" works, use "whom" — both end in m.

American English: periods and commas always inside quotation marks. British English: outside unless part of the quoted material.

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