1.
Grammatical is used to indicate that something relates to grammar.
Should the teacher present ~ rules to students?
...~ errors.
ADJ: ADJ n
~ly
...~ly correct language.
ADV: ADV adj/-ed
2.
If someone’s language is ~, it is considered correct because it obeys the rules of grammar.
...a new test to determine whether students can write ~ English.
ADJ
~ly
One in five undergraduates cannot write ~ly.
ADV: ADV after v