parker PAVC piston pump
Single stage pump – When a casing contains only one revolving impeller, it is called a single stage pump.
Double/multi-stage pump – When a casing contains two or more revolving impellers, it is called a double or multi-stage pump.
In biology, many different types of chemical and bio-mechanical pumps have evolved, and biomimicry is sometimes used in developing new types of mechanical pumps.