1. Pressure device: refers to containers, pipelines, safety accessories, and pressure accessories.

2. Container: refers to a container designed and manufactured to hold fluids under pressure, including accessories directly connected to nodes connecting other devices. Containers can be composed of multiple compartments.

3. Pipeline: refers to pipe fittings connected together to form a pressure system, used for transporting fluids.

4. Safety attachment: refers to a device designed to prevent pressure vessels from exceeding the allowable pressure.

5. Components: Refers to several pressure devices that are assembled by manufacturers into a complete unit with certain functions.

6. Fluid: Refers to gases, liquids, vapors, or their mixtures. Fluids can also contain suspended solids.

7. Permanent node: refers to a node that cannot be split without destruction.

8. Nominal size: refers to the size value including all components of the pipeline system, except for components indicated by external diameter or thread count.