Expendable means capable of being used up, replaced, or sacrificed without serious loss. When something is expendable, losing it won't cause major problems because you can get another one or do without it.

In movies about space missions or military operations, you might hear about “expendable supplies”: things like food packets, batteries, or fuel that the crew expects to use up and can't reuse. The opposite would be critical equipment that must be protected at all costs.

The word takes on a darker meaning when applied to people. Calling someone expendable suggests they could be replaced easily, that their individual value doesn't matter much. In a video game, you might have expendable characters who can be lost without affecting your mission.

You might hear someone say “I feel expendable” at school if they think their contributions to a group project don't matter, or that the group would work just as well without them. No one deserves to be treated that way.

Understanding what's expendable helps with planning and priorities. Before a camping trip, you might realize your fancy jacket is expendable but your water bottle isn't.