principal investigator vs PI

principal investigator and PI both are nouns.

Word	Noun	Adjective	Verb	Adverb
principal investigator	Yes	No	No	No
PI	Yes	No	No	No

As nouns, principal investigator and PI are synonyms defined as:

principal investigator and PI: the scientist in charge of an experiment or research project

principal investigator (noun)	PI (noun)
the scientist in charge of an experiment or research project	an antiviral drug used against HIV; interrupts HIV replication by binding and blocking HIV protease; often used in combination with other drugs
	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