Grammar · 62 pages
Grammar & writing mechanics
Discover essential English grammar rules with examples, guides on punctuation, and clear explanations for common word confusables — designed to answer your writing questions fast.
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All 62 grammar & writing mechanics pages
Affect vs effect
The difference is that affect is normally a verb meaning to influence or have an impact on something, while effect is normally a noun meaning the result or outcome produced. The rain affected the match; the rain had an effect on the match. The catch is the exceptions: effect can be a verb (to bring about, as in to effect change) and affect can be a noun in psychology (a person’s observable emotional state).
ComparisonIts vs it’s
The difference is that "its" without an apostrophe is the possessive determiner meaning belonging to it (the dog wagged its tail), while "it’s" with an apostrophe is the contraction of "it is" or "it has" (it’s raining; it’s been a long day). The reliable test is to expand the apostrophe version: if you can replace the word with "it is" or "it has" and the sentence still makes sense, use it’s; otherwise use its.
ComparisonYour vs you’re
The difference is that "your" is the possessive determiner meaning belonging to you (bring your notes), while "you’re" is the contraction of "you are" (you’re early). The reliable test is to expand the word to "you are": if the sentence still makes sense, write you’re with an apostrophe; if it does not, write the possessive your. The apostrophe in you’re only ever stands in for the missing letter in "are".
ComparisonWho vs whom
The difference is grammatical role. "Who" is a subject pronoun, used for the person performing the action (Who wrote this?), while "whom" is an object pronoun, used for the person receiving the action or following a preposition (To whom should I send it?). The classic test is to answer with he or him: if "he" fits, use who; if "him" fits, use whom — both whom and him end in m.
ComparisonActive vs passive voice
The difference is who does the work in the sentence. In the active voice the subject performs the action: "The cat chased the mouse." In the passive voice the subject receives the action, and the doer is moved to a "by" phrase or dropped: "The mouse was chased (by the cat)." The passive is formed with a form of the verb to be plus a past participle. Active voice is usually clearer and more direct; the passive is useful when the doer is unknown, unimportant or deliberately de-emphasised.
ComparisonThere, their, they’re
The difference is that these three are homophones with separate jobs. "There" points to a place or position, or starts a sentence (there is, there are). "Their" is the possessive determiner meaning belonging to them. "They’re" is the contraction of "they are". Tests: if you mean a location or "there is/are", use there; if something belongs to them, use their; if you can expand it to "they are", use they’re. The apostrophe in they’re marks the missing letter in are.
DefinitionPrepositional phrase
A prepositional phrase is a group of words beginning with a preposition and ending with a noun or pronoun called its object, together with any modifiers of that object. Examples include "in the morning", "under the old table", and "to her". The whole phrase works as a single unit, acting as an adjective or adverb to add information about time, place, direction, manner or detail.
DefinitionSubordinating conjunctions
Subordinating conjunctions are words that link a dependent clause to an independent clause, signalling the relationship between them — cause, time, condition, contrast and so on. Common examples are because, although, since, while, if, when, unless and after. The clause they introduce cannot stand alone as a sentence; it depends on the main clause to complete the meaning, as in "because it rained, we stayed inside".
DefinitionAdjective
An adjective is a word that describes or modifies a noun or pronoun, giving information about its qualities — what kind, which one, how many or whose. Examples include happy, three, red, ancient and British. Adjectives usually appear before the noun they describe (a red door) or after a linking verb (the door is red), and many can show degree through comparative and superlative forms (tall, taller, tallest).
DefinitionOxford comma
The Oxford comma, or serial comma, is the comma used before the final coordinating conjunction (and or or) in a list of three or more items: "red, white, and blue". Its purpose is to prevent ambiguity about how the last items group. It is not universally required: it is recommended by Oxford and Chicago style but dropped by most newspaper styles, including AP and much British journalism.
DefinitionApostrophe
An apostrophe is a punctuation mark used mainly to show possession or to indicate where letters have been left out in a contraction. We add ’s to show that something belongs to a singular noun (the child’s book) and an apostrophe alone to most plurals (the dogs’ kennels). In contractions, it marks omitted letters: do not becomes don’t, it is becomes it’s. It is not used to make ordinary plurals.
DefinitionComma
A comma is a punctuation mark that signals a short pause and separates parts of a sentence for clarity. Its main uses are listing items (red, white and blue), joining two independent clauses with a conjunction, setting off introductory words or phrases, and enclosing non-essential information. Used well, commas guide the reader; used wrongly, they create comma splices or change the meaning of a sentence.
DefinitionEm dash
An em dash ( — ) is a punctuation mark, the width of a capital M, used to signal a strong or abrupt break in a sentence. It can replace commas, parentheses or a colon to set off extra information, mark an interruption, or add emphasis: "The result — surprising as it was — held up." It is longer than the en dash (–), which marks ranges, and the hyphen (-), which joins compounds.
DefinitionColon
A colon ( : ) is a punctuation mark that introduces what follows: a list, an explanation, a quotation or an elaboration of the preceding statement. The words before a colon should normally form a complete independent clause, as in "She brought three things: a map, a torch and a flask." The colon points the reader forward, signalling that what comes next explains or completes the idea before it.
DefinitionQuestion mark
A question mark ( ? ) is the punctuation mark that ends a direct question — a sentence that asks something and expects a reply, such as "Where are you going?". It replaces the full stop at the end of the sentence. It is not used after an indirect question, which only reports that a question was asked ("She asked where I was going."), because that is a statement rather than a direct query.
DefinitionHyphen
A hyphen ( - ) is the shortest of the horizontal marks, used to join words or parts of a word into a single unit. It links compound adjectives before a noun (a well-known author), connects spelled-out numbers (thirty-five), and attaches certain prefixes (re-enter, ex-partner). It is shorter than the en dash (–), which marks ranges, and the em dash (—), which marks sentence breaks; the three are not interchangeable.
DefinitionSemicolon
A semicolon ( ; ) is a punctuation mark that joins two closely related independent clauses without a conjunction, or separates list items that themselves contain commas. It marks a pause stronger than a comma but weaker than a full stop. For example: "The experiment failed; the funding dried up." Each side of the semicolon could stand as its own sentence, which is what distinguishes correct use from a comma splice.
DefinitionParentheses
Parentheses ( ), known as round brackets in British English, are a pair of curved marks used to enclose information that is supplementary or non-essential — an aside, a clarification, an example or a reference. The sentence must still read correctly if the bracketed material is removed, as in "The results (see Table 2) were consistent." They signal a lower level of emphasis than commas or dashes would.
DefinitionNoun
A noun is a word that names a person, place, thing, animal, quality or idea. Examples include doctor, city, table, dog, honesty and freedom. Nouns can act as the subject or object of a sentence, can usually be made plural or possessive, and are often introduced by determiners such as a, the or my. They are one of the eight traditional parts of speech and form the backbone of most sentences.
DefinitionVerb
A verb is a word that expresses an action (run, write), an occurrence (happen, become) or a state of being (be, seem). It is the essential part of a clause: every complete sentence needs at least one verb. Verbs change form to show tense, person and number — walk, walks, walked, walking — and they may be main verbs carrying the meaning or auxiliary (helping) verbs such as have, be and do.
DefinitionAdverb
An adverb is a word that modifies a verb, an adjective, or another adverb, adding information about manner, time, place, frequency or degree. Examples include quickly, often, here, yesterday and very. Many adverbs are formed by adding -ly to an adjective (quick → quickly), but not all — fast, well and soon are adverbs without the ending. Adverbs answer questions such as how, when, where and to what extent.
DefinitionPronoun
A pronoun is a word that stands in for a noun or noun phrase to avoid repetition. Instead of "Maria said Maria was tired", we say "Maria said she was tired". Common pronouns include I, you, he, she, it, we, they, who, this and myself. The noun a pronoun replaces is called its antecedent, and the pronoun should agree with that antecedent in number, gender and person.
DefinitionPreposition
A preposition is a word that links a noun or pronoun to the rest of a sentence, showing a relationship of place (in, on, under), time (before, during, at), direction (to, towards, into) or other connections (of, with, for). The noun or pronoun that follows it is its object, and together they form a prepositional phrase, such as "on the table" or "after lunch".
DefinitionConjunction
A conjunction is a word that joins words, phrases or clauses within a sentence. The three main types are coordinating conjunctions (and, but, or), which link elements of equal rank; subordinating conjunctions (because, although, when), which attach a dependent clause to a main one; and correlative conjunctions (either…or, neither…nor), which work in pairs. Conjunctions let writers combine ideas instead of using only short, separate sentences.
DefinitionInterjection
An interjection is a word or phrase that expresses a sudden feeling or reaction, such as surprise, pain, joy or hesitation — for example wow, ouch, oh, hey and oops. It is grammatically independent: it does not connect to the rest of the sentence the way other parts of speech do, and it is often punctuated with a comma or an exclamation mark. Interjections are common in speech and informal writing but rare in formal prose.
DefinitionParts of speech
The parts of speech are the categories that classify every word by the function it performs in a sentence. English traditionally has eight: nouns (name things), pronouns (replace nouns), verbs (express action or being), adjectives (describe nouns), adverbs (modify verbs and more), prepositions (show relationships), conjunctions (join), and interjections (express emotion). Many grammars add a ninth, the determiner or article (a, the, this), for words that introduce nouns.
DefinitionVerb tenses
English has 12 verb tenses created by combining three time frames (past, present, future) with four aspects (simple, continuous, perfect, perfect continuous). Simple tenses state facts or habits. Continuous tenses show ongoing action. Perfect tenses connect two points in time. Perfect continuous tenses emphasise duration up to a reference point. Each tense has a distinct structure formula using auxiliaries such as have, be and will.
DefinitionTypes of sentences
There are four sentence types by purpose: declarative sentences state information, interrogative sentences ask questions, imperative sentences give commands or requests, and exclamatory sentences express strong emotion. By grammatical structure, sentences are classed as simple (one independent clause), compound (two independent clauses joined by a coordinating conjunction), complex (one independent plus one dependent clause), or compound-complex.
DefinitionCompound sentences
A compound sentence contains two or more independent clauses — groups of words that could each stand alone as a sentence — joined by a coordinating conjunction (for, and, nor, but, or, yet, so) or by a semicolon. A comma is placed before the coordinating conjunction. Because both clauses are independent and equal in rank, neither subordinates the other, which distinguishes a compound sentence from a complex sentence.
DefinitionComplex sentences
A complex sentence has one independent clause that can stand alone as a sentence and at least one dependent clause that cannot. The dependent clause is introduced by a subordinating conjunction (because, although, since, when, if, unless, after, while, etc.). When the dependent clause comes first, a comma follows it; when it comes second, no comma is usually needed. Complex sentences allow writers to show how ideas relate — cause, time, contrast, condition.
DefinitionSimple sentences
A simple sentence contains one and only one independent clause: a subject (who or what) and a predicate (what they do or are). Despite the name, it can be long, including multiple words or phrases describing the subject or action. What makes it "simple" is its single clause. Common structural patterns are S+V (She writes), S+V+O (She writes reports), S+V+C (The results are clear), and S+V+A (The team meets weekly).
DefinitionText structure
Text structure refers to the way a writer organises information within a text. The five main non-fiction text structures are: description (detailing characteristics), sequence or chronological order (ordering events or steps), compare and contrast (showing similarities and differences), cause and effect (linking actions to outcomes), and problem and solution (presenting a problem and its resolution). Recognising text structure aids comprehension and writing.
DefinitionArticles: a, an, the
English has three articles: a and an (indefinite, for non-specific or first-mention nouns) and the (definite, for specific, already-known or unique nouns). Use a before consonant sounds and an before vowel sounds. The zero article (no article) applies to plural countable nouns used generally, most proper nouns, and uncountable nouns in a general sense. Articles are among the most common sources of error for non-native English speakers.
DefinitionRun-on sentence
A run-on sentence incorrectly joins two independent clauses without proper punctuation or a coordinating conjunction. The most common type is the fused sentence, where no punctuation separates the clauses at all. Another type is the comma splice, where only a comma (without a conjunction) is used. There are four standard fixes: add a full stop and start a new sentence; add a semicolon; add a comma plus a coordinating conjunction; or restructure with a subordinating conjunction.
DefinitionSentence fragment
A sentence fragment lacks one or more elements required for a complete sentence: a subject, a main verb, or an independent clause. Fragments arise when a dependent clause is punctuated as if it were complete, when a phrase stands alone, or when a subject or verb is omitted. Most fragments can be fixed by attaching them to an adjacent sentence or by adding the missing element. Intentional fragments are used for stylistic effect in creative and informal writing.
DefinitionTopic sentence
A topic sentence announces the central idea of a paragraph in one clear statement, usually placed at or near the beginning. It controls what goes into the paragraph — all supporting sentences should develop, explain or illustrate the topic sentence's claim. Good topic sentences are specific enough to guide the paragraph, general enough to need supporting detail, and linked to the essay's or document's overarching argument or thesis.
ComparisonAdjective vs adverb
An adjective describes a noun or pronoun (a clear explanation, she is brilliant). An adverb modifies a verb, adjective or other adverb — and sometimes a whole clause (she writes clearly, an extremely clear explanation, very quickly). Many adverbs are formed by adding -ly to an adjective (quick → quickly), but not all -ly words are adverbs, and many adverbs have no -ly at all (fast, well, hard, late).
DefinitionDirect and indirect speech
Direct speech quotes exact words using quotation marks and a reporting verb: He said, "I will attend the conference." Indirect speech reports the meaning without quoting, shifting the tense back (backshift): He said that he would attend the conference. Pronouns and time expressions also change. Understanding both forms is essential for academic citation, journalism and formal writing.
DefinitionConditional sentences
English has five conditional types. Zero conditional states universal truths (If you heat water to 100 °C, it boils). First conditional describes real future possibilities (If she submits by Friday, the editor will review it). Second conditional covers hypothetical present or future situations (If she had more funding, she would expand the study). Third conditional describes unreal past situations (If they had checked the data, they would have caught the error). Mixed conditionals blend past and present (If she had taken the position, she would be leading the project now).
DefinitionTypes of conjunctions
The three types of conjunctions are: coordinating conjunctions (for, and, nor, but, or, yet, so — FANBOYS), which join grammatically equal elements; subordinating conjunctions (because, although, when, if, since, unless, after, while, etc.), which introduce dependent clauses; and correlative conjunctions (either...or, neither...nor, both...and, not only...but also), which work in matched pairs. Each type has distinct punctuation rules.
DefinitionPrepositions: complete reference list
A preposition is a word placed before a noun or pronoun (its object) to show a relationship with another part of the sentence. Common prepositions include in, on, at, by, with, under, over, between, through, about, after, before and during. Prepositions are grouped by the kind of relationship they express: time, place, direction, manner, cause and comparison. Complex prepositions are multi-word: according to, in spite of, because of.
ComparisonGerund vs infinitive
A gerund is a verb's -ing form used as a noun: "Finishing the report took three hours." An infinitive is to + the base verb used as a noun, adjective or adverb: "She hopes to finish the report." Many verbs are followed by only a gerund (enjoy, avoid, finish, deny, practise, suggest), others only by an infinitive (want, hope, refuse, decide, agree, manage), and some by both — with the same meaning (start, begin, continue, like, love) or a different meaning (remember, stop, try, regret).
DefinitionParallel structure in writing
Parallel structure requires matching grammatical forms when listing or comparing items. If one item in a list is a noun, all must be nouns; if one is an infinitive, all must be infinitives; if one is a clause, all must be clauses. Faulty parallelism — mixing forms — makes sentences harder to read and signals imprecision. Parallel structure is especially important with correlative conjunctions (both...and, either...or) and in lists.
DefinitionSentence structure
English sentence structure is organised around five core patterns: SV (Subject–Verb: she writes), SVO (Subject–Verb–Object: she writes reports), SVC (Subject–Verb–Complement: the results are clear), SVA (Subject–Verb–Adverbial: the team meets weekly), and SVOO (Subject–Verb–Indirect Object–Direct Object: she sent the committee the report). By clause count, sentences are simple, compound, complex or compound-complex. Varying structure creates clarity and rhythm.
DefinitionSubject-verb agreement
Subject-verb agreement requires the verb to match its subject in number: a singular subject takes a singular verb (he runs) and a plural subject takes a plural verb (they run). Tricky cases include collective nouns (the team is/are), indefinite pronouns (each is, none is or are), compound subjects joined by and or or, inverted sentences (here are the files), and relative clauses (the one who is responsible).
DefinitionTypes of pronouns
The nine types of pronoun in English are: personal (I, you, he, she, it, we, they), possessive (mine, yours, his, hers, ours, theirs), reflexive (myself, yourself, themselves), relative (who, which, that), interrogative (who, what, which), demonstrative (this, that, these, those), indefinite (everyone, someone, any, all, none), reciprocal (each other, one another), and intensive (I myself; she herself — for emphasis).
DefinitionCapitalisation rules
Capital letters are required for proper nouns (names, places, organisations, days, months and holidays), the first word of every sentence, titles used before a name (Dr Brown, President Smith), acronyms (NASA, UNESCO) and major words in titles of works. Seasons (spring, autumn), compass directions (drive north) and most common nouns are written in lower case.
DefinitionDangling modifier
A dangling modifier is a modifier whose intended subject is absent from the sentence or is not the grammatical subject of the main clause. For example, "Walking to school, it started to rain" — the participial phrase implies someone was walking, but the grammatical subject is it, not a person. The fix is to name the true doer as the subject: "Walking to school, I felt the rain begin to fall."
DefinitionMisplaced modifier
A misplaced modifier is a modifier positioned too far from its intended referent, causing the sentence to mean something other than intended. For example: "She almost drove her children to school every day" (almost should modify every day). The fix is to move the modifier immediately before or after the word it modifies. Misplaced differs from dangling: the referent exists but is in the wrong position.
DefinitionIndependent clause
An independent clause contains a subject and a predicate and expresses a complete thought, so it can stand alone as a sentence. Two independent clauses can be joined by a semicolon, by a comma followed by a co-ordinating conjunction (for, and, nor, but, or, yet, so — FANBOYS), or by a colon when the second explains the first. Two clauses joined without any punctuation form a fused or run-on sentence; joined by a comma alone, the error is called a comma splice.
DefinitionDependent clause
A dependent clause (also called a subordinate clause) has a subject and a finite verb but cannot stand alone, because it begins with a subordinating conjunction (because, although, when, if) or a relative pronoun (who, which, that). Types include adverbial clauses (modifying the verb), adjectival/relative clauses (modifying a noun) and noun clauses (acting as subject or object). A fronted dependent clause is followed by a comma; one that follows the main clause usually takes no comma.
DefinitionRelative clause
A relative clause is a dependent clause beginning with a relative pronoun (who, whom, whose, which, that) that modifies a noun in the main clause. Defining (restrictive) relative clauses identify which specific noun is meant and take no commas (the student who passed was awarded a prize). Non-defining (non-restrictive) relative clauses add extra information about a known noun and are enclosed in commas (Mr Smith, who teaches history, retired).
DefinitionSubordinate clause
A subordinate clause is a dependent clause introduced by a subordinating conjunction (because, although, when, if, unless, while, whereas) or a relative pronoun, giving it three types: adverbial (modifies the verb), adjectival/relative (modifies a noun) and noun (acts as subject or object). A complex sentence is an independent clause combined with one or more subordinate clauses. A fronted subordinate clause is followed by a comma; one that follows the main clause usually takes no comma.
DefinitionComma rules
The ten main comma rules are: (1) Oxford comma before the last item in a list; (2) before a co-ordinating conjunction joining independent clauses; (3) after an introductory element; (4) around a non-restrictive relative clause; (5) between co-ordinate adjectives; (6) after a transitional phrase (however, therefore); (7) separating geographical elements; (8) after salutation in a letter; (9) separating adjacent identical words; (10) marking contrast (not X, but Y).
DefinitionSemicolon rules
Semicolon rules: (1) join two closely related independent clauses without a conjunction (She studied all night; she still failed); (2) before a conjunctive adverb (however, therefore, moreover, consequently) joining two independent clauses — semicolon before, comma after; (3) separate list items that contain internal commas (We visited Paris, France; Rome, Italy; and Madrid, Spain). Never use a semicolon before a dependent clause or immediately after a co-ordinating conjunction.
ComparisonColon vs semicolon
The difference is function: a colon introduces what follows ("as follows" / "that is to say") — a list, explanation, elaboration or quotation — and must be preceded by a complete independent clause. A semicolon joins two independent clauses of equal weight without a conjunction, acting as a stronger comma or a weaker full stop. Neither substitutes for the other.
DefinitionApostrophe rules
Apostrophe rules cover two uses: possession and contractions. For possession: singular noun + 's (the dog's bowl); plural noun ending in s + ' (the dogs' bowls); plural not ending in s + 's (children's, women's); shared possession uses one apostrophe (Jack and Jill's house). For contractions: the apostrophe replaces missing letters (it's = it is; you're = you are; they're = they are). Apostrophes are never used for simple plurals: CDs, 1990s, MPs.
DefinitionPronoun-antecedent agreement
Pronoun-antecedent agreement requires a pronoun to match its antecedent in number (singular/plural) and gender. Singular antecedents take singular pronouns: everyone brought his or her laptop (or, now widely accepted, their laptop — singular they). Collective noun antecedents follow number in context. Compound antecedents joined by and take plural pronouns; joined by or/nor, the pronoun matches the nearest antecedent.
DefinitionSAT grammar rules
The top 10 SAT grammar rules tested are: (1) subject-verb agreement; (2) pronoun-antecedent agreement; (3) pronoun case (who vs whom); (4) verb tense consistency; (5) modifier placement (dangling and misplaced); (6) parallel structure; (7) comma usage (splice, introductory clause, Oxford comma); (8) apostrophes (its/it's; your/you're); (9) word choice (affect/effect; fewer/less); (10) sentence boundaries (fragments, run-ons, comma splices).
DefinitionEnglish grammar rules
The most important English grammar rules are: subject-verb agreement (verb matches subject in number); verb tense consistency (no unmotivated tense shifts); pronoun agreement (pronoun matches antecedent); comma rules (Oxford comma, introductory clause, splice); apostrophes (possession and contractions only, not plurals); sentence structure (avoid fragments and run-ons); modifier placement (adjacent to the word modified); parallel structure; and correct article use (a/an/the).
DefinitionCompound-complex sentence
A compound-complex sentence is the fourth sentence type in English. It contains two or more independent clauses (as in a compound sentence) plus one or more dependent clauses (as in a complex sentence). Example: "Although he was tired, he finished the assignment, and he submitted it on time." It enables writers to express several related ideas and their logical connections in a single, well-constructed sentence — essential for advanced academic and professional prose.
ComparisonIndependent vs dependent clause
The difference is completeness. An independent clause has a subject and predicate and expresses a complete thought — it can stand alone as a sentence. A dependent clause also has a subject and predicate but is made grammatically incomplete by a subordinating conjunction (because, although, when) or relative pronoun (who, which, that), so it cannot stand alone. Punctuating a dependent clause as a sentence is a fragment error.
