Question

Now that you have worked through a lot of material that includes these basic patterns, and you have compared grammatically correct and incorrect sentences, write down what you think is a rule that could explain what makes a sentence grammatically correct or not. For example, you might write something like: "verbs always match nouns in number, and they usually come before the noun." In other words, make your best guess for the grammar rule that makes sense out of the pattern(s) you see in the phrases you have been working with. Review if you need to, and you might briefly check your hunches against the sentences you have been working with in this or previous modules. Keep in mind that what you're after is your hunch, not a grammar rule from a text book. Now check your hunch with the explanation of this principle in the following pattern.

Answer 1

Here’s a compact hunch about what makes an English sentence grammatical, followed by quick checks against common patterns.

Hunch / rule
- A sentence is grammatical when its parts are arranged in the language’s normal phrase-structure order (in English typically Subject–Verb–Object) and the relevant words agree in grammatical features (number, person, tense, case, and the syntactic categories that verbs require). In other words: correct order + matching grammatical features + correct types of complements = grammatical sentence.

How that accounts for patterns (checks)
- Subject–verb agreement: The finite verb must match the subject in number/person.
- Grammatical: She walks. (singular subject → walks)
- Ungrammatical: *She walk. (verb doesn’t agree)
- Word order (SVO): Changing the canonical order usually produces ungrammaticality unless other grammatical processes apply (passivization, topicalization, inversion).
- Grammatical: The dog chased the cat.
- Ungrammatical: *Chased the dog the cat. (wrong order)
- Case for pronouns: Subjects require nominative case; objects require objective case.
- Grammatical: He saw her.
- Ungrammatical: *Him saw she. (wrong case)
- Subcategorization (selection): Verbs require specific types/number of complements.
- Grammatical: She put the book on the table. (transitive + prepositional complement)
- Ungrammatical/incomplete: *She put. (put needs an object/location)
- Tense/auxiliary structure: Auxiliaries and tense morphology must appear in the correct slots and agree with clause type (questions, negatives, conditionals).
- Grammatical question: Did she go? (auxiliary inversion)
- Ungrammatical: *She did go? (wrong order for a yes/no question unless marked prosodically)
- Agreement beyond number: Determiners, quantifiers, and some adjectives constrain noun phrases.
- Grammatical: These apples are ripe.
- Ungrammatical: *This apples is ripe. (determiner/number mismatch)

Limitations / notes
- English allows some flexibility (passives, topicalization, clefts, ellipsis), so surface order alone isn’t enough; you must consider whether a grammatical operation licenses the deviation.
- Some “ungrammatical” strings are acceptable in casual speech or certain dialects, but the general rule predicts the standard-grammar judgements most of the time.

Summary
- The simple, testable hunch: correct constituency and order plus matching grammatical features and appropriate complements explain why many sentences are judged grammatical or not. Checking the common patterns (agreement, case, word order, and verb complementation) confirms this principle.