dengue fever vs breakbone fever

dengue fever and breakbone fever both are nouns.

Word	Noun	Adjective	Verb	Adverb
dengue fever	Yes	No	No	No
breakbone fever	Yes	No	No	No

As nouns, dengue fever and breakbone fever are synonyms defined as:

dengue fever and breakbone fever: an infectious disease of the tropics transmitted by mosquitoes and characterized by rash and aching head and joints

Other synonyms of dengue fever include dandy fever, dengue.

dengue fever (noun)	breakbone fever (noun)
an infectious disease of the tropics transmitted by mosquitoes and characterized by rash and aching head and joints	an infectious disease of the tropics transmitted by mosquitoes and characterized by rash and aching head and joints