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English UsageComparison guide

Installment vs. Instalment

“Installment” and “instalment” are standard regional variants. “Installment” is the usual U.S. spelling, while “instalment” is chiefly British usage.

ReviewedEvidence2 sourcesSectionEnglish Usage
Quick answer

Use “installment” in U.S. English and “instalment” in British English, unless your house style chooses differently.

Key details

Confusion Familyregional spelling
Rule Familyregional-usage
TermsInstallment, Instalment

Further guidance

Core difference

The two spellings normally represent the same noun; the difference is regional.

Usage Boundary

Choose the spelling expected by the audience or house style and keep it consistent.

Sources and evidence

Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.

  1. Installment — Cambridge Dictionary (opens in a new tab)Cambridge Dictionary · US spelling evidence for installment
  2. Instalment — Cambridge Dictionary (opens in a new tab)Cambridge Dictionary · Mainly UK spelling evidence for instalment

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