0 a small backpack (= a bag used to carry things on your back), used especially when travelling or walking -- 日用背包,小背包
Keep a photocopy of your passport in your daypack at all times for identification purposes.
The bag doubles as a wheeled suitcase and a backpack - a daypack detaches for use in the car or on the plane.
If you have balance problems, it might help to do more hiking with just a small daypack, because a big pack can make everything feel less stable.
A climber found a day pack of a woman who disappeared five or six years ago.