milk pox vs smallpox

milk pox and smallpox both are nouns.

Word	Noun	Adjective	Verb	Adverb
milk pox	Yes	No	No	No
smallpox	Yes	No	No	No

As nouns, smallpox is a hypernym of milk pox; that is, smallpox is a word with a broader meaning than milk pox:

milk pox: a mild form of smallpox caused by a less virulent form of the virus
smallpox: a highly contagious viral disease characterized by fever and weakness and skin eruption with pustules that form scabs that slough off leaving scars

Other hypernyms of milk pox include variola, variola major.

milk pox (noun)	smallpox (noun)
a mild form of smallpox caused by a less virulent form of the virus	a highly contagious viral disease characterized by fever and weakness and skin eruption with pustules that form scabs that slough off leaving scars