English grammar is the set of structural rules of the English language. This includes the structure of words, phrases, clauses, sentences, and whole texts.

This article describes a generalized, present-day Standard English – forms of speech and writing used in public discourse, including broadcasting, education, entertainment, government, and news, over a range of registers, from formal then to informal. Divergences from the grammar described here occur in some historical, social, cultural, and regional varieties of English, although these are minor compared to the differences in pronunciation and vocabulary.

Modern English has largely abandoned the inflectional case system of Indo-European in favor of analytic constructions. The personal pronouns retain morphological case more strongly than any other word class (a remnant of the more extensive Germanic case system of Old English). For other pronouns, and all nouns, adjectives, and articles, grammatical function is indicated only by word order, by prepositions, and by the "Saxon genitive or English possessive" (-'s).

Nouns, verbs, adjectives, and adverbs are open classes – word classes that readily accept new members, such as the noun celebutante (a celebrity who frequents the fashion circles). The rest are closed classes; for example, it is rare for a new pronoun to enter the language. Determiners, traditionally classified along with adjectives, have not always been regarded as a separate part of speech. Interjections are another word class, but these are not described here as they do not form part of the clause and sentence structure of the language.

Linguists generally accept nine English word classes: nouns, verbs, adjectives, adverbs, pronouns, prepositions, conjunctions, determiners, and exclamations. English words are not generally marked for word class. It is not usually possible to tell from the form of a word which class it belongs to, but some inflectional endings and derivational suffixes are distinct to each class. On the other hand, most words belong to more than one word class. For example, run can serve as either a verb or a noun (these are regarded as two different lexemes). Lexemes may be inflected to express different grammatical categories. The lexeme run has the forms runs, ran, runny, runner, and running. Words in one class can sometimes be derived from those in another. This has the potential to give rise to new words. For example, the noun aerobics has given rise to the adjective aerobicized.

Words combine to form phrases. A phrase typically serves the same function as a word from some particular word class. For example, my very good friend Peter is a phrase that can be used in a sentence as if it were a noun, and is therefore called a noun phrase. Similarly, adjectival phrases and adverbial phrases function as if they were adjectives or adverbs, but with other types of phrases, the terminology has different implications. For example, a verb phrase consists of a verb together with any objects and other dependents; a prepositional phrase consists of a preposition and its complement (and is therefore usually a type of adverbial phrase); and a determiner phrase is a type of noun phrase containing a determiner.

Many common suffixes form nouns from other nouns or from other types of words, such as -age (shrinkage), -hood (sisterhood), and so on, though many nouns are base forms containing no such suffix (cat, grass, France). Nouns are also created by converting verbs and adjectives, as with the words talk and reading (a boring talk, the assigned reading).

Nouns are sometimes classified semantically (by their meanings) as proper and common nouns (Cyrus, China vs frog, milk) or as concrete and abstract nouns (book, laptop vs embarrassment, prejudice). A grammatical distinction is often made between count (countable) nouns such as clock and city, and non-count (uncountable) nouns such as milk and decor. Some nouns can function both as countable and as uncountable such as "wine" in This is a good wine.