Grammar & Punctuation Crash Course | Research

This is a reference guide covering the essential 20% of grammar and punctuation rules that handle 80% of cases. Bookmark it.

The Complete Sentence

Every sentence needs three things:

Subject — who or what the sentence is about
Verb — what happens
Complete thought — makes sense on its own

Missing any of these = fragment. Having two complete thoughts improperly joined = run-on.

Parts of Speech

The eight parts of speech: noun, pronoun, verb, adjective, adverb, preposition, conjunction, interjection.

You need to know four main ones cold:

Part	What it does	Examples
Noun	Names a person, place, thing, or idea	dog, Paris, freedom
Verb	Expresses action or state of being	run, think, is, become
Adjective	Describes a noun	tall, blue, interesting
Adverb	Describes a verb, adjective, or other adverb	quickly, very, extremely

Adjectives vs. Adverbs

This is where people trip up.

Adjectives modify nouns: “a fast car,” “the blue sky”
Adverbs modify verbs, adjectives, or other adverbs: “drives quickly,” “very tall”

The -ly rule (usually):

Most adverbs are formed by adding -ly to an adjective:

quick → quickly
careful → carefully
easy → easily (y → ily)

But not always:

Some adjectives end in -ly: friendly, lovely, lonely
Some adverbs don’t use -ly: fast, hard, well

The Linking Verb Trap

Linking verbs (is, am, are, was, were, seem, feel, look, taste, smell) connect the subject to a description. Use adjectives after linking verbs, not adverbs.

Wrong: I feel badly about it.
Right: I feel bad about it. (describes "I")

Wrong: The soup tastes deliciously.
Right: The soup tastes delicious. (describes "soup")

Wrong: She looks beautifully.
Right: She looks beautiful. (describes "she")

Test: If the verb can be replaced with “is/am/are,” use an adjective.

Good vs. Well / Bad vs. Badly

This trips up everyone.

Good = adjective (describes nouns)
Well = adverb (describes verbs) — except when referring to health

Wrong: She sings good.
Right: She sings well. (how does she sing?)

Right: She has a good voice. (what kind of voice?)

Right: I don't feel well. (health = exception, well is adjective here)

Same pattern for bad/badly:

Wrong: He plays bad.
Right: He plays badly.

Right: That's a bad idea. (what kind of idea?)

Comparatives and Superlatives

Comparing two things → comparative (-er or more) Comparing three+ things → superlative (-est or most)

Syllables	Comparative	Superlative
1 syllable	taller	tallest
2 syllables ending in -y	happier	happiest
2+ syllables	more beautiful	most beautiful

Never double up:

Wrong: more taller, most fastest
Right: taller, fastest

Irregular forms (memorize these):

good → better → best
bad → worse → worst
far → farther/further → farthest/furthest
little → less → least
many/much → more → most

Articles (a, an, the)

A = before consonant sounds: a dog, a university (sounds like “yoo”)
An = before vowel sounds: an apple, an hour (silent h)
The = specific thing already known

I saw a dog. The dog was brown.
     ↑ first mention   ↑ now we know which one

Prepositions

Show relationships (location, time, direction): in, on, at, to, for, with, by, from, about, between, through, during, before, after.

The book is on the table.
I'll meet you at noon.
She walked through the door.

Rule: A preposition is always followed by a noun or pronoun (its object), never a verb.

Conjunctions

Join words, phrases, or clauses.

Coordinating (FANBOYS): for, and, nor, but, or, yet, so

I wanted to go, but I was tired.

Subordinating: because, although, when, if, since, while, after, before, unless

I left because I was tired.
Although it rained, we went anyway.

Correlative (pairs): both…and, either…or, neither…nor, not only…but also

Both the dog and the cat are sleeping.
Either you leave or I will.

Subject-Verb Agreement

Singular subjects take singular verbs. Plural subjects take plural verbs.

He runs. (singular)
They run. (plural)

The Tricky Cases

Prepositional phrases don’t change the subject:

The box of chocolates is on the table.
   ↑ subject (singular)    ↑ verb (singular)

Not “are” — ignore “of chocolates.”

Compound subjects with “and” are plural:

Tom and Jerry are fighting.

“Or” / “nor” — verb matches the nearer subject:

Either the cats or the dog is responsible.
Neither the dog nor the cats are responsible.

Collective nouns (team, crowd, jury) are usually singular:

The team is winning.

Indefinite pronouns (everyone, anyone, each, nobody) are singular:

Everyone is here.
Each of the students has a book.

Comma Rules

1. Before Coordinating Conjunctions (FANBOYS)

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

I wanted to go, but the weather was terrible.
             ↑ comma before "but"

Only when both sides are complete sentences. No comma needed here:

I wanted to go but couldn't. (second part isn't a complete sentence)

2. After Introductory Elements

After the movie, we went home.
However, I disagree.
Running late, she grabbed her keys.

3. Around Nonessential Information

If you can remove it and the sentence still makes sense, use commas:

My brother, who lives in Boston, is visiting.
            ↑ nonessential ↑

No commas if essential:

The man who lives next door is a doctor.
(Which man? The one who lives next door — essential info)

Quick test: Can you remove it? If yes → commas. If no → no commas.

4. In Lists (The Oxford Comma)

I bought apples, oranges, and bananas.
                        ↑ Oxford comma (optional but recommended)

The Oxford comma prevents ambiguity:

I love my parents, Batman and Wonder Woman. (Are your parents superheroes?)
I love my parents, Batman, and Wonder Woman. (Clear: three separate entities)

5. Direct Address

John, are you coming?
I think, Sarah, you're right.
Let's eat, Grandma. (vs. "Let's eat Grandma.")

Semicolons, Colons, and Dashes

Semicolon (;)

Joins two related independent clauses without a conjunction:

I have a meeting at noon; I'll be back by two.

Also used with transitional words (however, therefore, nevertheless):

I wanted to help; however, I was too busy.

Colon (:)

Introduces what follows — a list, explanation, or elaboration:

I need three things: coffee, silence, and time.
She had one goal: finish the book.

Rule: What comes before the colon must be a complete sentence.

Em Dash (—)

The Swiss Army knife of punctuation. Can replace commas, colons, or parentheses for emphasis:

She had only one option—run.
My brother—the tall one—is visiting.

Use sparingly. One or two per piece of writing.

Apostrophes

Contractions

Apostrophe replaces missing letters:

don't = do not
it's = it is
who's = who is

Possessives

Singular: Add ‘s

the dog's tail
James's book (or James' book — both acceptable)

Plural ending in s: Add just ’

the dogs' tails
the students' papers

Plural not ending in s: Add ‘s

the children's toys
the men's room

Never for Plurals

Wrong: The Smith's are coming.
Right: The Smiths are coming.

Wrong: I have three dog's.
Right: I have three dogs.

The Confusables

Its vs. It’s

It’s = it is / it has (contraction)
Its = belonging to it (possessive)

It's raining. (It is raining.)
The dog wagged its tail. (The tail belonging to the dog.)

Test: Substitute “it is.” If it works → it’s. If not → its.

Your vs. You’re

You’re = you are
Your = belonging to you

You're late. (You are late.)
Your coat is on the chair.

Their vs. They’re vs. There

They’re = they are
Their = belonging to them
There = location / existence

They're coming to the party.
Their car is blue.
The book is over there.
There are three options.

Affect vs. Effect

Affect = verb (to influence)
Effect = noun (the result)

The weather affects my mood.
The effect was immediate.

Memory trick: Affect = Action (both start with A). Effect = End result (both start with E).

Fewer vs. Less

Fewer = countable things
Less = uncountable quantities

Fewer cars, fewer people, fewer dollars
Less traffic, less energy, less money

Lay vs. Lie

Lay = to put/place something (requires an object)
Lie = to recline (no object)

Lay the book on the table.
I need to lie down.

Past tense trap: The past tense of “lie” is “lay.”

Yesterday I lay in bed until noon. (past tense of lie)
Yesterday I laid the book down. (past tense of lay)

Who vs. Whom

Who = subject (doing the action)
Whom = object (receiving the action)

Who is calling? (He is calling.)
Whom should I contact? (I should contact him.)

Test: Substitute he/him. “He” → who. “Him” → whom.

Parallel Structure

Items in a list or comparison must have the same grammatical form.

Wrong: I like running, swimming, and to bike.
Right: I like running, swimming, and biking.

Wrong: She is smart, talented, and works hard.
Right: She is smart, talented, and hardworking.

Check for parallelism whenever you use “and” or “or.”

Modifiers

Misplaced Modifiers

Modifiers should be next to what they modify:

Wrong: Covered in chocolate, I ate the strawberries.
Right: I ate the strawberries covered in chocolate.

Dangling Modifiers

The thing being modified must actually be in the sentence:

Wrong: Walking to school, the rain started.
(Who's walking? Not the rain.)

Right: Walking to school, I got caught in the rain.

Run-Ons and Fragments

Run-On / Comma Splice

Two complete sentences incorrectly joined:

Wrong: I love coffee, it keeps me awake. (comma splice)
Wrong: I love coffee it keeps me awake. (fused sentence)

Four fixes:

Period: I love coffee. It keeps me awake.
Semicolon: I love coffee; it keeps me awake.
Comma + conjunction: I love coffee, and it keeps me awake.
Subordination: I love coffee because it keeps me awake.

Fragments

Incomplete sentences:

Fragment: Because I was tired.
Complete: I went to bed because I was tired.

Fragment: Running down the street.
Complete: She was running down the street.

Test: Read it aloud. Does it sound complete? Would a stranger understand it without more context?

Quick Reference Card

Rule	Example
Comma before FANBOYS joining clauses	I ran, and she walked.
Comma after intro elements	After lunch, we left.
Semicolon joins related clauses	I came; I saw; I conquered.
Colon introduces lists/explanations	I need: milk, eggs, bread.
Apostrophe for contractions	don’t, it’s, who’s
Apostrophe for possession	dog’s tail, dogs’ tails
Never apostrophe for plurals	The dogs are running.
Subject-verb must agree	Everyone is here.
Modifiers next to what they modify	I saw a man with binoculars.
Parallel structure in lists	eating, sleeping, and reading
Adjectives modify nouns	a tall building
Adverbs modify verbs (often -ly)	runs quickly
Use adjective after linking verb	I feel bad (not badly)
good/well, bad/badly	She sings well. It’s a good song.
Comparatives: -er or more	taller, more beautiful
Superlatives: -est or most	tallest, most beautiful