secondary school vs Gymnasium

secondary school and Gymnasium both are nouns.

Word	Noun	Adjective	Verb	Adverb
secondary school	Yes	No	No	No
Gymnasium	Yes	No	No	No

As nouns, secondary school and Gymnasium are synonyms defined as:

secondary school and Gymnasium: a school for students intermediate between elementary school and college; usually grades 9 to 12

Other synonyms of secondary school include lycee, lyceum, middle school.

secondary school (noun)	Gymnasium (noun)
a school for students intermediate between elementary school and college; usually grades 9 to 12	a school for students intermediate between elementary school and college; usually grades 9 to 12