Definition
In a jet engine compressor or turbine, a stage is one matched pair consisting of a row of rotating blades (a rotor) followed by a row of stationary blades (a stator, or vanes). Each stage adds a small increment of pressure rise in the compressor, or extracts a small amount of energy in the turbine. Multiple stages are arranged in series to achieve the total pressure ratio or energy extraction the engine requires.
Plain English
A stage is one rotating disk of blades plus the fixed row of blades right behind it. Jet engines have many of these pairs lined up one after the other, each doing a little bit of the work of squeezing or extracting energy from the air.
Context Anchor
Seen when studying jet engine airflow, especially the compressor and turbine sections of the engine.
Derivation
From the Old French 'estage' meaning a level, floor, or step. The aviation use keeps that idea: each stage is one step in a sequence, with the air being worked on a little more at every step.
Why Pilots Care
The number of stages determines how much overall pressure rise or power extraction the engine can achieve, which directly affects thrust, fuel efficiency, and operating limits.
Intuition Check
Stages does not mean phases of flight here. In jet engine basics, stages are internal steps in the engine, usually blade sections, that handle the air or hot gas in sequence.
Example Sentence 1
The compressor in this turbofan has fourteen stages, each adding a small amount of pressure to the airflow before it reaches the combustion chamber.
Example Sentence 2
Hot gases pass through the turbine stages and give up energy to spin the compressor and fan.