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frame; framework
border; box
limit; restriction; quota
category; bracket; class
time slot (in a broadcasting schedule)
stream; livestream; live stream; live (online) broadcast
spool (of thread); reel
決められた枠内で予算を組む必要がある。
Budget within the predetermined limits.
写真の枠を新しくした。
I replaced the photo frame.
応募の枠がすでに埋まっていたので参加できなかった。
The application slots were already full, so I couldn't participate.