再開 and 再生: resuming an activity and playing a recording
Compare resuming an interrupted class with playing a recording, keeping media playback distinct from a restarted meeting.
Starting an interrupted activity again
再開, read さいかい, means resuming an interrupted activity. 休憩後、授業を再開しました。 says that the class resumed after a break.
工事を来月再開する予定です。 says that resuming construction next month is planned. A plan is distinct from a report that work has already resumed.
Playing recorded sound or video
再生, read さいせい, is used for playing recordings or video. 昨日の録音を再生しました。 says that yesterday’s recording was played.
動画の再生を一時停止しました。 says that video playback was paused. Here 再生 refers to the operation of the video.
Identifying what starts again
会議の録音を再生しました。 says that a recording of the meeting was played. It does not report that participants assembled again or resumed the meeting.
This guide covers media playback. Other contexts may use 再生 for regeneration or recovery; identify the object before interpreting it as operating a playback control.
Does 会議の録音を再生しました。 establish that the meeting started again?
Show the answer and why
No. It says that the meeting recording was played. Resumption of the meeting itself requires separate information.