General Certificate of Secondary Education vs O level

General Certificate of Secondary Education and O level both are nouns.

Word	Noun	Adjective	Verb	Adverb
General Certificate of Secondary Education	Yes	No	No	No
O level	Yes	No	No	No

As nouns, General Certificate of Secondary Education and O level are synonyms defined as:

General Certificate of Secondary Education and O level: the basic level of a subject taken in school

Other synonyms of General Certificate of Secondary Education include GCSE.

General Certificate of Secondary Education (noun)	O level (noun)
the basic level of a subject taken in school	the basic level of a subject taken in school