conserve

verb (used with object), con·served, con·serv·ing.

1. to prevent injury, decay, waste, or loss of: Conserve your strength for the race.
2. to use or manage (natural resources) wisely; preserve; save: Conserve the woodlands.
3. Physics, Chemistry. to hold (a property) constant during an interaction or process: the interaction conserved linear momentum.
4. to preserve (fruit) by cooking with sugar or syrup.