Rigor or rigour?

In American English write rigor; in British and Commonwealth English, rigour. rigor is a noun meaning “US spelling of rigour”; rigour is a noun meaning “Severity or strictness”. In written English (wordfreq, 2021 data) rigor is about 2.5 times as common as rigour.

rigororrigour

What is the difference between rigor and rigour?

	rigor	rigour
Part of speech	noun	noun
Meaning	USUS spelling of rigour informalEllipsis of rigor mortis	Severity or strictness Harshness, as of climate
Example	none recorded	none recorded
Forms	rigors	rigours
Pronunciation	/ˈɹɪɡə/ /ˈɹɪɡɚ/	/ˈɹɪɡə(ɹ)/
Region	US	no label
In writing	1.2 times per million words	about once in every 2 million words

Sources: rigor and rigour in the English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0); written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media).

Every current meaning of rigor and rigour

rigor

1
noun USUS spelling of rigour
2
noun informalEllipsis of rigor mortis

rigour

1
noun Severity or strictness
2
noun Harshness, as of climate
3
noun A feeling of cold with shivering accompanied by a rise in body temperature
4
noun Character of being unyielding or inflexible
5
noun Shrewd questioning
6
noun Higher level of difficulty

Source: the English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0); obsolete, archaic, dialect and rare senses left out.

Which is more common, rigor or rigour?

rigor appears 1.2 times per million words; rigour about once in every 2 million words.

0.0010.010.11101001,00010,000

rarerper million words of written Englishmore common

rigor 1.2 times per million wordsrigour about once in every 2 million words

Source: written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media).

How many people search rigor vs rigour?

“rigor vs rigour” is searched about 110 times a month on Google and 30 on Bing in the United States. Google counts close variants of a query together (“rigour vs rigor”, “rigor or rigour”).

Sources: Google Ads keyword data through DataForSEO and Microsoft Advertising keyword data through DataForSEO, the average month from September 2025 to August 2026.