- dad, dada, daddy, pa, papa, pappa, pater, pop - an informal term for a father; probably derived from baby talk
--1 is a kind of step; father, male parent, begetter; step; father, male parent, begetter
- protactinium, protoactinium, Pa, atomic number 91 - a short-lived radioactive metallic element formed from uranium and disintegrating into actinium and then into lead
--2 is a kind of metallic element, metal; metallic element, metal
- pascal, Pa - a unit of pressure equal to one newton per square meter
--3 is a kind of pressure unit; pressure unit
- Pennsylvania, Keystone State, PA - a Mid-Atlantic state; one of the original 13 colonies
--4 is a kind of American state; American state
--4 is a part of Mid-Atlantic states
--4 has parts: - public address system, P.A. system, PA system, P.A., PA - an electronic amplification system used as a communication system in public areas
--5 is a kind of communication system; communication system
--5 has parts:amplifier; loudspeaker, speaker, speaker unit, loudspeaker system, speaker system; tannoy