Definition
The ability of a material to retain magnetism after the magnetizing force has been removed. A material with high retentivity holds its magnetism strongly; one with low retentivity loses it quickly once the external magnetic field is gone.
Plain English
How well a material stays magnetized after you stop magnetizing it. Some materials hold onto magnetism for a long time; others let it fade almost immediately.
Context Anchor
Seen in aircraft maintenance discussions of magnetism, electrical parts, and materials that may keep unwanted magnetism.
Derivation
From the Latin retinere, meaning 'to hold back' or 'to keep.' A material with retentivity 'keeps' the magnetism it was given.
Why Pilots Care
Determines the long-term strength and reliability of permanent magnets used in compasses, magnetos, and other aircraft systems.
Analogy
Think of retentivity like a sponge holding water after you lift it out of the sink. A high-retentivity sponge stays soaked; a low-retentivity sponge drains right away.
Intuition Check
Retentivity is not the force that magnetizes the material. It is the magnetism the material keeps after that force is gone.
Example Sentence 1
Permanent magnets used in aircraft magnetos are made from alloys with high retentivity so they hold their magnetic strength over many years of operation.
Example Sentence 2
High-retentivity alloys are chosen for aircraft magnetos so the magnetic field stays strong over time.