conserve -- (keep constant through physical or chemical reactions or evolutionary change; "Energy is conserved in this process")
conserve, preserve, maintain, keep up -- (keep in safety and protect from harm, decay, loss, or destruction; "We preserve these archeological findings"; "The old lady could not keep up the building"; "children must be taught to conserve our national heritage"; "The museum curator conserved the ancient manuscripts")
conserve, husband, economize, economise -- (use cautiously and frugally; "I try to economize my spare time"; "conserve your energy for the ascent to the summit")
conserve -- (preserve with sugar; "Mom always conserved the strawberries we grew in the backyard")