Armor vs. Armour
“Armor” is the standard US spelling; “armour” is the standard UK spelling of the same word. Do not treat one form as universally wrong: the choice is regional orthography, including in compounds such as body armor/body armour.
“Armor” is the standard US spelling; “armour” is the standard UK spelling of the same word.
Key details
Choose the right form
| Audience/style | Preferred spelling | Compounds |
|---|---|---|
| US English | armor | body armor, armored |
| UK English | armour | body armour, armoured |
| mixed/international document | follow house style | keep related forms consistent |
Quick tests
Regional spelling test
Is the document using US or UK spelling conventions?
If yes: Use “armor” for US English or “armour” for UK English, including related forms where the house style calls for them.
If no: If the audience is international, choose a consistent house convention rather than labeling one regional form wrong.
Caveat: The two spellings name the same word; the distinction is orthographic and regional, not semantic.
Examples
The exhibit includes medieval armor.
US spelling.
The museum restored a suit of armour.
UK spelling.
The article uses “armor” in one paragraph and “armour” in the next without explanation.
Better: Use one regional spelling convention consistently.
Both forms are valid, but unexplained mixing is a style inconsistency.
Further guidance
Core difference
“Armor” is the standard US spelling; “armour” is the standard UK spelling of the same word.
Fast Test
Choose the spelling required by the document’s regional or house style and keep it consistent.
Usage Boundary
Do not treat one form as universally wrong: the choice is regional orthography, including in compounds such as body armor/body armour.
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.
- Armor — Cambridge Dictionary (opens in a new tab)Cambridge University Press · Direct dictionary evidence identifying armor as the US spelling of armour.
- Armour — Cambridge Dictionary (opens in a new tab)Cambridge University Press · Direct dictionary evidence identifying armour as the UK spelling corresponding to US armor.