PI vs Norvir

PI and Norvir both are nouns.

Word	Noun	Adjective	Verb	Adverb
PI	Yes	No	No	No
Norvir	Yes	No	No	No

As nouns, Norvir is a hyponym of PI; that is, Norvir is a word with a more specific, narrower meaning than PI:

PI: an antiviral drug used against HIV; interrupts HIV replication by binding and blocking HIV protease; often used in combination with other drugs
Norvir: a protease inhibitor (trade name Norvir) used in treating HIV

Other hyponyms of PI include Crixivan, indinavir, nelfinavir, Viracept, ritonavir, Invirase, saquinavir.

PI (noun)	Norvir (noun)
an antiviral drug used against HIV; interrupts HIV replication by binding and blocking HIV protease; often used in combination with other drugs	a protease inhibitor (trade name Norvir) used in treating HIV
someone who can be employed as a detective to collect information and assist in criminal investigations
the scientist in charge of an experiment or research project