Grammatically means according to the rules of grammar: the system that governs how words fit together to form clear, correct sentences. When something is written or spoken grammatically, it follows the patterns and conventions of the language.

Grammar includes things like subject-verb agreement (saying “she runs” instead of “she run”), proper punctuation, correct word order, and choosing the right verb tenses. A sentence can be grammatically correct even if it's awkward or unclear, as long as it follows these rules. For instance, “The purple elephant danced on Mars” is grammatically correct, even though it describes something unrealistic.

Teachers often talk about whether student writing is grammatically sound, meaning it follows the rules properly. When you revise an essay, you might ask yourself: “Is this sentence grammatically correct?” You're checking whether you've structured it according to English grammar rules.

Sometimes people confuse grammatical correctness with good writing. A sentence can be grammatically perfect but still boring or confusing. The best writing is both grammatically correct and clear, interesting, and well-organized. Think of grammar as the foundation of a house: you need it to be solid, but the foundation alone doesn't make the house beautiful or comfortable to live in.