heart vs medical center

heart and medical center both are nouns.

Word	Noun	Adjective	Verb	Adverb
heart	Yes	No	No	No
medical center	Yes	No	No	No

As nouns, medical center is a hyponym of heart; that is, medical center is a word with a more specific, narrower meaning than heart:

heart (noun)	medical center (noun)
a playing card in the major suit that has one or more red hearts on it	the part of a city where medical facilities are centered
the courage to carry on
an inclination or tendency of a certain kind
the hollow muscular organ located behind the sternum and between the lungs; its rhythmic contractions move the blood through the body
the locus of feelings and intuitions
the choicest or most essential or most vital part of some idea or experience
a positive feeling of liking
a firm rather dry variety meat (usually beef or veal)
an area that is approximately central within some larger region
a plane figure with rounded sides curving inward at the top and intersecting at the bottom; conventionally used on playing cards and valentines