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screw
key (of a clock, watch, etc.); spring
ドライバーでねじをしっかり締めた。
I tightened the screw firmly with a screwdriver.
この家具はねじが足りなくて組み立てられない。
I can't assemble this furniture because screws are missing.
ねじが緩んでいたので締め直しておいた。
The screw was loose so I tightened it again.