heliotropism vs tropism

heliotropism and tropism both are nouns.

Word	Noun	Adjective	Verb	Adverb
heliotropism	Yes	No	No	No
tropism	Yes	No	No	No

As nouns, tropism is a hypernym of heliotropism; that is, tropism is a word with a broader meaning than heliotropism:

heliotropism: an orienting response to the sun
tropism: an involuntary orienting response; positive or negative reaction to a stimulus source

heliotropism (noun)	tropism (noun)
an orienting response to the sun	an involuntary orienting response; positive or negative reaction to a stimulus source