Plain English Meaning
An old-style electronic tube with five working parts inside it. It was used to make weak electrical signals stronger, such as in early radios and radio receivers in aircraft.
Full Definition
A vacuum tube containing five active electrodes: a cathode, a control grid, a screen grid, a suppressor grid, and a plate (anode). The added grids reduce unwanted internal effects found in simpler tubes, allowing the pentode to amplify weak signals more efficiently and at higher frequencies than a triode or tetrode.
Context Anchor
Seen in older aircraft radio, communication, navigation, and electronic equipment descriptions, especially in maintenance or historical systems.
Derivation
From the Greek 'pente' meaning 'five' and '-ode' from 'electrode.' The name simply tells you how many electrodes are inside: five.
Why Pilots Care
Most modern pilots will not operate a pentode directly, but the term can appear in older avionics manuals or maintenance references. Knowing it identifies an electronic tube helps keep the discussion from being confused with a switch, wire, or modern solid-state part.
Intuition Check
Do not read “pentode” as simply any device with five outside terminals. In this context, it specifically means a vacuum tube with five internal working electrodes.
Example Sentence 1
The pentode in the old aircraft receiver had to be replaced when the radio's reception became weak and noisy.
Example Sentence 2
Early navigation receivers used a pentode stage to boost incoming signals.