British Guiana vs Guyana

British Guiana and Guyana both are nouns.

Word	Noun	Adjective	Verb	Adverb
British Guiana	Yes	No	No	No
Guyana	Yes	No	No	No

As nouns, British Guiana and Guyana are synonyms defined as:

British Guiana and Guyana: a republic in northeastern South America; formerly part of the British Empire, but it achieved independence from the United Kingdom in 1966

Other synonyms of British Guiana include Co-operative Republic of Guyana.

British Guiana (noun)	Guyana (noun)
a republic in northeastern South America; formerly part of the British Empire, but it achieved independence from the United Kingdom in 1966	a republic in northeastern South America; formerly part of the British Empire, but it achieved independence from the United Kingdom in 1966