This sentence is extremely complex in its grammatical structure.这个句子的语法结构极为复杂。

Dialogue often breaks grammatical rules.对话经常会违反语法规则。

grammatical errors语法错误

a test to determine whether students can write grammatical English考查学生英语写作是否符合语法规则的测试

This sentence is not grammatical.这个句子不符合语法规则。