one of several parts into which a story, plan, or amount of money owed has been divided, so that each part happens or is paid at different times until the end or total is reached

The novel has been serialized for radio in five instalments. 这部小说已在电台进行了5次分期播送。

We agreed to pay for the car by/in instalments. 我们同意分期付款购买小汽车。