piping and instrumentation diagram/drawing (P&ID) is defined by the Institute of Instrumentation and Control as follows:
A diagram which shows the interconnection of process equipment and the instrumentation used to control the process. In the process industry, a standard set of symbols is used to prepare drawings of processes. The instrument symbols used in these drawings are generally based on International Society of Automation (ISA) Standard S5. 1.
The primary schematic drawing used for laying out a process control installation.