This is the 3045th most frequent Arabic word.
الإنكليزي
"الإنكليزي" means "the English" (referring to the English language or English people).
Here, "الإنكليزي" describes the type of literature, indicating that it pertains to the English language or culture.
أحب قراءة الأدب الإنكليزي.
I enjoy reading English literature.
In this sentence, "الإنكليزية" (a form of "الإنكليزي") modifies "قواعد اللغة," specifying that it is the grammar of the English language.
درست قواعد اللغة الإنكليزية في المدرسة.
I studied English grammar at school.
The word "الإنكليزية" relates to the ability to converse in the English language.