Question

Prompt
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

Hunch (in one sentence)
- A sentence is grammatical when words are combined in the right structural relationships (which words head which phrases) and when dependent words share the right features (number, person, tense) with their heads — not just because the words appear in some order.

Check and brief explanation of the principle
- The core idea behind this principle is structure dependency plus feature agreement:
- Structure dependency: English sentences are built from nested constituents (phrases). Rules operate on constituents (e.g., subject phrase, verb phrase), not on a simple left-to-right string of words. That is why moving or changing a whole constituent is grammatical, while changing a single word in the same position can be ungrammatical.
- Feature agreement: Certain elements (e.g., verbs and subjects, auxiliaries and tense, determiners and nouns in some languages) must share matching grammatical features (number, person, tense). If features don’t match, the sentence is ungrammatical.
- Selection/subcategorization: Heads (verbs, prepositions) require particular types or numbers of complements (transitive verbs need objects, intransitive verbs don’t), and violating those requirements makes a sentence bad.

Short examples showing how the principle explains correctness/incorrectness
- Subject–verb agreement (feature matching):
- Correct: The cat is on the mat. (singular subject + singular verb)
- Incorrect: *The cat are on the mat. (number mismatch → ungrammatical)
- Structure dependency (constituents, not linear order):
- Correct question formation: What did the man eat? (auxiliary do moves to front of clause containing the verb phrase)
- Incorrect: *What ate the man? (if intended meaning was same as above, this incorrectly moves lexical verb rather than auxiliary — structure, not just word order, matters)
- Selection/subcategorization:
- Correct: She put the book on the table. (put requires a direct object + PP)
- Incorrect: *She put on the table. (missing required object → ungrammatical in the intended meaning)
- Pronoun binding (structural relation):
- Correct: John_i said he_i would come. (pronoun can refer to subject in proper structural position)
- Incorrect/odd: *He_i said John_i would come. (depends on intended reading; structure affects which antecedents are available)

Conclusion
- Your hunch that matching and order matter is on the right track, but it’s more accurate to say grammar enforces relationships defined by hierarchical structure plus feature matching and selectional requirements. These three components together predict why many sentences are grammatical or not.