This is the 396th most frequent Finnish word.
englannin
"Englannin" means "of English" or "English (as a possessive or descriptive form)."
Here, 'englannin' is used as a possessive case referring to 'the English language,' where it indicates belonging or relation to English.
Pidän englannin kielestä koska se on kansainvälinen kieli.
I like the English language because it is an international language.
In this context, 'englannin' functions as an attribute defining what kind of teacher is being referred to—an English teacher.
Hänen englannin opettajansa on todella taitava.
Her English teacher is very skilled.
Here, 'englannin' specifically modifies 'kielen' to denote the subject of the lessons—English language lessons.