- Mustache and moustache are both correct spellings of the same word.
- Mustache is the most common spelling in the United States.
- Moustache is is used in other English-speaking countries.
- Mustachio is usually spelled without an “o” in the first syllable, although in the UK it is commonly written as a plural: mustachios.
From the pencil mustache of John Waters to the bushy moustache of General Melchett, upper-lip hair comes in variety of styles. It also comes in two different spellings.
Mustache vs. Moustache: What’s the Difference?
The difference between a mustache and moustache is only in the variety of English that’s used to spell it. In American English, the preferred spelling is the one without the o—mustache—although moustache is sometimes used as well. An American might write something like this:
In the United Kingdom, and in other parts of the world where English is more like the British variant than the American one, the preferred spelling is the one containing an o—moustache. A Brit might write:
Occasionally, people use mustachios to refer to large or elaborate mustaches. It’s common to drop the s in the United States:
A common slang term for mustache is stache. In Australia, however, they call a moustache a mo, and we have this slang term to thank for the word Movember.
Mustache in the US
Moustache Outside the US
Am I not denying other barbers the opportunity to cut my hair, shave my chin, and perhaps clip my mustachio?
The tears ran down his cheeks, and the drops hung on his mustachios – but not a muscle was distorted.
Mustache is not the only word that’s spelled differently in American English and British English. Some words lose an u in American English, like color; others lose an l, like canceled; and there are those spellings, like cheque, which are very different in American English.
from Grammarly Blog https://www.grammarly.com/blog/mustache-moustache/