opening; aperture (e.g. camera)
opening one's mouth; beginning to speak
open; broad
建物は南側に大きく開口している。
The building has a large opening on its south side.
彼は緊張しながらも、ついに開口し、質問をした。
Despite his nervousness, he finally opened his mouth and asked a question.
彼は開口一番、予算削減を発表した。
He immediately opened the meeting by announcing the budget cut.