rubella vs three-day measles

rubella and three-day measles both are nouns.

Word	Noun	Adjective	Verb	Adverb
rubella	Yes	No	No	No
three-day measles	Yes	No	No	No

As nouns, rubella and three-day measles are synonyms defined as:

rubella and three-day measles: a contagious viral disease that is a milder form of measles lasting three or four days; can be damaging to a fetus during the first trimester

Other synonyms of rubella include epidemic roseola, German measles.

rubella (noun)	three-day measles (noun)
a contagious viral disease that is a milder form of measles lasting three or four days; can be damaging to a fetus during the first trimester	a contagious viral disease that is a milder form of measles lasting three or four days; can be damaging to a fetus during the first trimester