Originally Posted By Jimshaw
By your definition my entire first aid kit, photon light, spare batteries, etc, are backup because they never get used but are carried anyhow.


Yeah, that's mostly correct, by my definition. Here's the two dictionary definitions I would reference to support it:

1. a thing that supports or reinforces another. (ie. First Aid, and First Aid Kits)

2. a device, etc., kept in reserve to serve as a substitute, if needed. (ie. spare batteries)

Dictionary.com > Backup

The above items could also be defined as "Essential" items.

Certainly backup items can be essential, or not (as in the case of your foam sleeping pad).

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