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beginning and end
doing something from beginning to end; being unchanged from beginning to end
from beginning to end; the whole time; throughout; consistently
交渉は終始穏やかな雰囲気で進んだ。
The negotiations proceeded in a calm atmosphere throughout.
彼は会議の間終始無言を貫いていた。
He remained silent throughout the entire meeting.
彼は終始笑顔で対応した。
He responded with a smile the whole time.