typhus vs rat typhus

typhus and rat typhus both are nouns.

Word	Noun	Adjective	Verb	Adverb
typhus	Yes	No	No	No
rat typhus	Yes	No	No	No

As nouns, rat typhus is a hyponym of typhus; that is, rat typhus is a word with a more specific, narrower meaning than typhus:

typhus: rickettsial disease transmitted by body lice and characterized by skin rash and high fever
rat typhus: acute infection caused by rickettsia and transmitted by the bite of an infected flea; characterized by fever and chills and muscle aches and a rash

Other hyponyms of typhus include endemic typhus, murine typhus, urban typhus.

typhus (noun)	rat typhus (noun)
rickettsial disease transmitted by body lice and characterized by skin rash and high fever	acute infection caused by rickettsia and transmitted by the bite of an infected flea; characterized by fever and chills and muscle aches and a rash