installment

• instalment (Commonwealth)

enPR: ĭn-stôlʹmənt,

• (UK) IPA^(key): /ɪnˈstɔːl.mənt/

  • Audio (Southern England)

    (file)

• (US) IPA^(key): /ɪnˈstɔl.mənt/
• (cot–caught merger) IPA^(key): /ɪnˈstɑl.mənt/
• (General Australian) IPA^(key): /ɪnˈstoːl.mənt/

A 1732 alteration of estallment, from Anglo-Norman estaler (“fix payments”), from Old French estal (“fixed position”), from Old High German stal (“stall", "standing place”)

The sense of "part of a whole produced in advance of the rest" is from 1823.

installment (plural installments) (American spelling)

1. 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.
   • 1861, E. J. Guerin, Mountain Charley, page 20:

     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.

   • 2009, Richard Leviton, Santa Fe Light: Touring the Visionary Geography of Santa Fe, New Mexico, →ISBN:

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

   • 2014, Karen Lee-Thorp, A Compact Guide to the Christian Life, →ISBN:

     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.

   • 2015, How to Write About Music, →ISBN, page 193:

     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. (banking, finance) One member of a series of portions of a debt or sum of money, which portions may or may not be equated (depending in part on whether the interest rate is fixed or variable), payment of which portions are serially exacted at regularly scheduled intervals toward satisfaction of the total. Payments of installments are generally mensual, quarterly, triannual, biannual, or annual.
3. (publishing, media) A part of a published or broadcast serial.
   • 2010, Michael A. Cramer, Medieval Fantasy as Performance, →ISBN, page ix:

     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.

   • 2012, Charles W. Chesnutt, The Marrow of Tradition, →ISBN:

     It is a serial story which we are all reading, and which grows in vital interest with each successive installment.

For this sense in the UK, the OED permits only the spelling instalment. Commonwealth usage varies.

• (portion of a debt):
• (part of a broadcast or published serial): episode, part

• installment loan
• installment plan

From install +‎ -ment, install from Old French installer, from Medieval Latin installare, from Medieval Latin in- and Medieval Latin stallum, stall from a Germanic source (compare Old High German stal).

installment (plural installments) (American spelling)

1. The act of installing; installation.
   • 1649, J[ohn] M[ilton], The Tenure of Kings and Magistrates: […], London: […] Matthew Simmons, […], published 1649 (2nd printing), →OCLC:

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

   • 2000, Rebecca Neason, Guises of the Mind, →ISBN, page 183:

     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.

2. (obsolete) The seat in which one is placed.
   • c. 1597 (date written), William Shakespeare, “The Merry Wiues of Windsor”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, →OCLC, [Act V, scene v]:

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

• investiture, investment
• installation

• “installment”, in Webster’s Revised Unabridged Dictionary, Springfield, Mass.: G. & C. Merriam, 1913, →OCLC.
• Webster's Seventh New Collegiate Dictionary, Springfield, Massachusetts, G.&C. Merriam Co., 1967
• Douglas Harper (2001–2024) “installment”, in Online Etymology Dictionary.