Grammar & writing definitions

29 grammar & writing terms from Achievable exam prep courses, each defined in plain language with links into the course textbook.

• A vs. anUse "a" before words that begin with a consonant sound and "an" before words that begin with a vowel sound. The choice depends on pronunciation, not spelling — "an hour" but "a university."
• AdjectiveAn adjective is a word that describes or modifies a noun or pronoun, answering questions like which one, what kind, or how many — for example, "red," "careful," or "three."
• ApostropheAn apostrophe (') is a punctuation mark used to show possession (the dog's leash) and to mark omitted letters in contractions (don't, it's). It is never used to make an ordinary noun plural.
• AppositiveAn appositive is a noun or noun phrase placed next to another noun to rename or describe it, as in "my sister, a nurse, works nights." Nonessential appositives are set off with commas; essential ones are not.
• Body paragraphA body paragraph is one of the middle paragraphs of an essay, sitting between the introduction and conclusion. Each one develops a single supporting point with a topic sentence, evidence, and analysis.
• Colon (punctuation)A colon (:) is a punctuation mark that follows a complete sentence to introduce a list, explanation, example, or quotation. What comes before a colon must be able to stand alone as a sentence.
• Comma before 'so'Use a comma before 'so' when it joins two independent clauses as a coordinating conjunction (meaning 'therefore'). Skip the comma when 'so' means 'so that,' introducing a purpose rather than a result.
• Comma spliceA comma splice is a sentence error in which two independent clauses are joined by only a comma, as in "I studied all night, I still failed." It is fixed with a period, semicolon, or comma plus a coordinating conjunction.
• ConjunctionA conjunction is a word that connects words, phrases, or clauses — such as and, but, or, because. English has three main types: coordinating, subordinating, and correlative conjunctions.
• DictionDiction is a writer's or speaker's choice of words. In literature, diction shapes tone, style, and meaning — the same idea can sound formal, casual, technical, or poetic depending on the words the author selects.
• FANBOYS (coordinating conjunctions)FANBOYS is a mnemonic for the seven coordinating conjunctions in English: for, and, nor, but, or, yet, and so. These words join grammatically equal elements — including two complete sentences when paired with a comma.
• GerundA gerund is a verb form ending in -ing that functions as a noun in a sentence, as in "Swimming is great exercise." Because it acts as a noun, a gerund can serve as a subject, object, or object of a preposition.
• Introductory adverbAn introductory adverb is an adverb or adverbial phrase placed at the start of a sentence to set up the main clause, and it is normally followed by a comma. Examples include "However," "Suddenly," and "After the game," at the beginning of a sentence.
• Its vs. it's"Its" (no apostrophe) is the possessive form of "it," while "it's" (with apostrophe) is a contraction of "it is" or "it has." If you can replace the word with "it is," use it's; otherwise, use its.
• Main ideaThe main idea is the central point a passage or paragraph communicates — the single claim everything else in the text supports. Identifying it is a core skill on reading tests like the SAT, ACT, and Praxis.
• Misplaced modifiersA misplaced modifier is a word or phrase positioned so far from the word it describes that the sentence becomes unclear or unintentionally describes the wrong thing. The fix is to move the modifier next to what it actually modifies.
• Modal verbsModal verbs are auxiliary verbs — can, could, may, might, must, shall, should, will, and would — that express ability, permission, possibility, obligation, or intention. They are always followed by the base form of the main verb.
• ParallelismParallelism is the principle that items in a series or in a paired construction must share the same grammatical form. "She likes hiking, swimming, and running" is parallel; "She likes hiking, swimming, and to run" is not.
• Parts of speechThe parts of speech are the categories that classify words by the job they do in a sentence: noun, pronoun, verb, adjective, adverb, preposition, conjunction, and interjection. Knowing a word's part of speech tells you how it can combine with other words.
• Pronoun casePronoun case is the form a pronoun takes based on its grammatical role in a sentence. English pronouns have three cases: subjective (I, he, she, we, they), objective (me, him, her, us, them), and possessive (my, his, her, our, their).
• Pronoun-antecedent agreementPronoun-antecedent agreement is the grammar rule that a pronoun must match the noun it refers to (its antecedent) in number, person, and gender. A singular antecedent takes a singular pronoun; a plural antecedent takes a plural pronoun.
• SemicolonA semicolon (;) is a punctuation mark that joins two closely related independent clauses without a conjunction. It also separates items in a list when the items themselves contain commas.
• Sentence fragmentA sentence fragment is a group of words punctuated as a sentence that does not express a complete thought. It is missing a subject, a verb, or an independent clause that can stand on its own.
• Sentence interruptionsA sentence interruption is a word or phrase inserted into a sentence that adds extra, nonessential information. It must be set off by a matching pair of commas, dashes, or parentheses, and the sentence must still work grammatically if the interruption is removed.
• Subject-verb agreementSubject-verb agreement is the grammar rule that a verb must match its subject in number: singular subjects take singular verbs, and plural subjects take plural verbs. Test questions hide the mismatch by separating the subject from the verb.
• SyntaxSyntax is the arrangement of words and phrases into sentences — the rules and choices that govern word order, sentence length, and structure. Writers use syntax deliberately to create emphasis, rhythm, and tone.
• Text structureText structure is the way a writer organizes ideas within a passage — the pattern that determines what comes first, what follows, and how the parts relate. Common structures include chronological order, cause and effect, compare and contrast, problem and solution, and description.
• Transition wordsTransition words are words and phrases — like furthermore, however, and therefore — that show the logical relationship between sentences or ideas. They signal whether a writer is adding, contrasting, giving an example, or drawing a conclusion.
• Verb tensesVerb tenses are the forms a verb takes to show when an action happens — in the past, the present, or the future. English combines three time frames with simple, progressive, perfect, and perfect progressive aspects to produce twelve tenses.