PROCESS CONTROL, Wikipedia
Process control is an engineering discipline that deals with architectures, mechanisms and algorithms for maintaining the output of a specific process within a desired range. For instance, the temperature of a chemical reactor may be controlled to maintain a consistent product output.

Process control is extensively used in industry and enables mass production of consistent products from continuously operated processes such as oil refining, paper manufacturing, chemicals, power plants and many others. Process control enables automation, by which a small staff of operating personnel can operate a complex process from a central control room.

PROCESS CONTROL SYSTEM, DCS or ICS
Process automation is an example of a distributed control system - the computer networking of electronic devices designed to monitor and control industrial production processes.

More often called a Distributed Control System (DCS) or an Industrial Control System (ICS) is a Process Control System is a computer server/client based system with input and output signals typically used in industries such as electrical, water, oil, gas and data. Process Control Systems are typically used to automate production activities. Based on data received from remote stations, automated or operator-driven supervisory commands can be pushed to remote station control devices, which are often referred to as field devices. Field devices control local operations such as opening and closing valves and breakers, collecting data from sensor systems, and monitoring the local environment for alarm conditions.

PROCESS CONTROL NETWORK, Wikipedia
A Process Control Network (PCN) is a communications network that is used to transmit instructions and data between control and measurement units and Supervisory Control and Data Acquisition (SCADA) equipment.These networks have, over the years, used many of the technologies and topologies utilised in other network applications. However, Process Control Networks (PCNs) have several special requirements that must be met in order for the solution to be acceptable to the industry.