1. (

• pi

) the ratio of the circumference to the diameter of a circle; approximately equal to 3.14159265358979323846... ;

2. (

• private_detective ,
• PI ,
• private_eye ,
• private_investigator ,
• operative ,
• shamus ,
• sherlock

) someone who can be employed as a detective to collect information ;

3. (

• principal_investigator ,
• PI ,

) the scientist in charge of an experiment or research project ;

4. (

• pi

) the 16th letter of the Greek alphabet ;

5. (

• protease_inhibitor ,
• PI

) an antiviral drug used against HIV; interrupts HIV replication by binding and blocking HIV protease; often used in combination with other drugs ;