a grammatical error的用法和样例：
- I stumbled across a grammatical error in your composition.
- The gay kindergarten teacher was furious when the school board rejected the books again because two were out of print and the third had a grammatical error in it.
- In general, a grammatical clause contain a subject and a predicate.
- That is not a grammatical sentence.
- He can barely form a grammatical sentence.
- There are many grammatical errors in his composition.