houseman vs Dr.

houseman and Dr. both are nouns.

Word	Noun	Adjective	Verb	Adverb
houseman	Yes	No	No	No
Dr.	Yes	No	No	No

As nouns, Dr. is a hypernym of houseman; that is, Dr. is a word with a broader meaning than houseman:

houseman: an advanced student or graduate in medicine gaining supervised practical experience
Dr.: a licensed medical practitioner

Other hypernyms of houseman include doc, doctor, MD, medico, physician.

houseman (noun)	Dr. (noun)
an advanced student or graduate in medicine gaining supervised practical experience	a licensed medical practitioner
	a person who holds Ph.D. degree (or the equivalent) from an academic institution