installment

noun

1. (US)One of a series of parts, whether equal or unequal to the other parts of the series, of a given entity or a given process, which part presents or is presented at a particular scheduled interval.

   “Not to give rise to suspicion, I drank when they were looking, and when able to do it unperceived, I quietly deposited the contents, by installments, under the table.”

   “Granted, this was but the first installment in the long process of “hatching” and mastering a dragon egg, but it was a good start.”

   “The blessings of the kingdom (healing, freedom, Stan's defat, abundant life, relationship with the King) are available now. Yet they are available only as a foretaste, the first installment of what will come when Christ returns.”

   “Now bands like Mumford and the Lumineers are fulfilling that role, but they're also becoming the latest installment of the whole "indie goes mainstream"/"mainstream co-opt indie" thing that's been happening since Seth Cohen's heyday -- or, you know, since Don Draper married Megan.”

2. (US)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.
3. (US)A part of a published or broadcast serial.

   “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.”

4. (US)The act of installing; installation.

   “Take oaths from all kings and magistrates at their installment, to do impartial justice by law.”

   “In the twenty-two years Faellon had been Chief Servant, he had officiated at many royal ceremonies, including the burial of Joakal's father and mother, and Joakal's own installment as King nine years ago.”

5. (US, obsolete)The seat in which one is placed.

   “Each faire Instalment, Coate, and seu’rall Crest, With loyall Blazon, euermore be blest.”