Translation guide
In Japanese, referring to a British person is usually done with イギリス人 (Igirisu-jin). The term 'Briton' is formal and rare in English, and its direct equivalent ブリトン人 is not commonly used. Instead, use the standard term for a British person.
Briton
Standard term for a British person. 'Briton' is formal/rare in English; this is the natural Japanese equivalent.
Referring to a person from Britain or the UK in everyday contexts.
The standard, neutral word for a British person. Covers English, Scottish, Welsh, and Northern Irish people collectively.
He is British.
I have a British friend.
More formal or written term for a British person. Often used in news or official contexts.
That British author is famous.
Direct transliteration of 'Briton', but very rare and unnatural in Japanese. Avoid using this; use イギリス人 instead.
This word is not commonly used and may not be understood. Stick to イギリス人.
He is said to be a Briton, but normally we say British person.
Referring to the Celtic inhabitants of Britain before and during the Roman period.
The English word 'Briton' is formal and rarely used in everyday speech. In Japanese, the natural equivalent is イギリス人. Using ブリトン人 for a modern British person sounds unnatural and may cause confusion. Reserve ブリトン人 for historical ancient Britons only.
He is British. (NOT 彼はブリトン人です。)
The ancient Britons were under the rule of the Roman Empire.