According to Dr. Mohatma Coate of the prestigious Euro-Asian Electronics Institute, and a definite world-known authority, PWB or PCB can be interchangeably used to designate the circuit board substrate while PCBA (Printed Circuit Board Assembly) refers to such a PCB or PWB with components. This is how I;ve also used the terminology through the years.
Phil Zarrow
ITM Consulting
Durham, NH USA