Plain English Meaning
A small helper device that takes a weak signal and turns it into the strong, precise movement needed to actually do the work — like a power assist that does the heavy lifting on command.
Full Definition
A small device that uses a low-power input signal to control a much larger output force or movement. In aircraft systems, a servo receives a command (electrical, hydraulic, or mechanical) and produces the physical motion needed to move a control surface, valve, or other component.
Context Anchor
Seen in autopilot, trim, and aircraft control-system descriptions.
Derivation
From the Latin servus, meaning 'slave' or 'servant.' The idea is that the device serves a command — it does the work on behalf of a small input signal. This is why automated control systems are called 'servo' systems: they obediently carry out the input they are given.
Why Pilots Care
Enables precise handling of large or high-speed aircraft where manual forces alone would be insufficient or fatiguing.
Intuition Check
A servo is not the autopilot itself. It is one powered part the system may use to move a control or hold a selected position.
Example Sentence 1
When the autopilot was engaged, the pitch servo gently moved the elevator to hold altitude.