preventive vs impediment

preventive and impediment both are nouns.

Word	Noun	Adjective	Verb	Adverb
preventive	Yes	Yes	No	No
impediment	Yes	No	No	No

As nouns, impediment is a hypernym of preventive; that is, impediment is a word with a broader meaning than preventive:

Other hypernyms of preventive include impedimenta, obstructer, obstruction, obstructor.

preventive (noun)	impediment (noun)
remedy that prevents or slows the course of an illness or disease	any structure that makes progress difficult
an agent or device intended to prevent conception	something immaterial that interferes with or delays action or progress
any obstruction that impedes or is burdensome

preventive (adjective)	impediment (adjective)
tending to prevent or hinder
preventing or contributing to the prevention of disease