1A notebook or pocket diary used to write down schedules, notes, or memos (a planner).
毎朝手帳にその日の予定を書き込む。
I write down the day's schedule in my planner every morning.
新しい手帳を買って来年の予定を整理した。
I bought a new planner and organized next year's schedule.
手帳を忘れるとスケジュールが管理しにくい。
If I forget my planner, it's hard to manage my schedule.
2Abbreviated usage referring to an official certificate/booklet (e.g., a disability certificate booklet).
身体障害者手帳を役所で申請した。
I applied for a disability certificate at the municipal office.
3Abbreviated usage meaning an identification booklet or badge used for official identification (e.g., a police ID booklet).
警察官が職務質問の際に警察手帳を見せた。
The police officer showed his police ID during a stop-and-question.