1. (

• dad ,
• dada ,
• daddy ,
• pa ,
• papa ,
• pappa ,
• pop

) an informal term for a father; probably derived from baby talk ;

2. (

• protactinium ,
• protoactinium ,
• Pa ,
• atomic_number_ ,

) a short-lived radioactive metallic element formed from uranium and disintegrating into actinium and then into lead ;

3. (

• pascal ,
• Pa

) a unit of pressure equal to one newton per square meter ;

4. (

• Pennsylvania ,
• Keystone_State ,
• PA ,
• Pa.

) a Mid-Atlantic state; one of the original 13 colonies ;

5. (

• public_address_system ,
• P.A._system ,
• PA_system ,
• P.A. ,
• PA

) an electronic amplification system used as a communication system in public areas ;