reserve
n. C / Un. a supply of something that you keep so you can use it later if you need it. It can also mean an area of land where animals and plants are protected.
n. a supply of a commodity or asset not needed for immediate use but available if required. Often refers to protected natural areas or a quality of shy, restrained behavior in social contexts.
The country has a large reserve of oil.
The central bank maintains a significant foreign currency reserve to stabilize the economy during market volatility.
While the nature reserve provides a sanctuary for endangered species, the local government must balance conservation efforts with the growing demand for sustainable tourism infrastructure.
From Old French reserver, from Latin reservō (“to reserve, retain”).
Often used in the plural ('reserves') when referring to natural resources or funds. When referring to a person's shy character, it is usually uncountable.