installment

1. (banking, finance) Any of a series of portions of a debt or sum of money, which portions may or may not be equal in amount (depending in part on whether the interest rate is fixed or variable), and payment of which takes place at regular intervals toward satisfaction of the total. Payments are generally mensual, quarterly, triannual, biannual, or annual.US

2. (publishing, media) A part of a published or broadcast serial.Examples: "With The Two Towers, the new installment of the Lord of the Rings trilogy, about to storm the box office, we are seeing what might be called the enchanting of America."; "It is a serial story which we are all reading, and which grows in vital interest with each successive installment."Synonyms: episode, partUS