suffix, godan verb (-ku)
Suffix that attaches to nouns or adjectival stems to form a godan verb meaning 'to become (that state/condition)'. Often used in set expressions; not freely productive. Related to 付く (つく) sense 14.
See also: 付く (つく)
彼は最近、落ち着いてきた。大人づいてきたのかもしれない。
He has become calmer lately. Maybe he's grown up a bit.
この辺りもすっかり都会づいてきた。
This area has become quite urbanized.