An intransitive verb meaning to become deeper, stronger, or more intense—used for emotions, understanding, relationships, etc.
夜が更けるにつれて、雨の気配が深まった。
As the night progressed, the feeling that it would rain deepened.
議論が進むにつれて両者の対立は深まった。
As the discussion went on, the conflict between the two deepened.
理解が深まることで、問題の解決策が見えてきた。
As understanding deepened, solutions to the problem became apparent.