undersecretary vs secretary

undersecretary and secretary both are nouns.

Word	Noun	Adjective	Verb	Adverb
undersecretary	Yes	No	No	No
secretary	Yes	No	No	No

As nouns, secretary is a hypernym of undersecretary; that is, secretary is a word with a broader meaning than undersecretary:

undersecretary: a secretary immediately subordinate to the head of a department of government
secretary: a person who is head of an administrative department of government

undersecretary (noun)	secretary (noun)
a secretary immediately subordinate to the head of a department of government	a desk used for writing
	an assistant who handles correspondence and clerical work for a boss or an organization
	a person who is head of an administrative department of government
	a person to whom a secret is entrusted