Sombre and somber describe the same thing — serious and gloomy in mood, or dark and muted in colour — and the only difference is which side of the Atlantic you're writing for. British English uses sombre, as in "The mood at the funeral was understandably sombre," while American English uses somber.
The core difference
Sombre and somber share one meaning; British writing takes the -re spelling, American writing takes -er.
- sombre — serious and gloomy, or dark and dull in colour or light: A sombre grey light filled the room before the storm broke.
- somber — the American spelling of the same word: The mood in the room turned somber once the results came through.
Which spelling should you use?
Both spellings trace back to the French sombre, "dark," possibly from the Latin sub umbra, "under shade." British English kept the French -re ending, matching other borrowings like centre and theatre, while American English regularised it to -er.
The word covers two related senses: a gloomy, serious mood, as in a sombre account of bad news, and a dark, muted colour or light, as in sombre grey clouds. Both senses take the same spelling split, so there is no need to switch spellings between the two meanings.
