The act or or the right to hold a position, property, asset in your possession for a given period of time is called a tenure.
During this period you are legally protected from the uncertainty or pressure of being asked to let go your position or property unless you break any terms of the contract.

Example:
If you rent a room and the agreement is made for 1 year then this one year is known as tenure. In this time, unless the terms of contract are broken, the property remains in your possession