Definition
In chemistry and metallurgy, a substance combined with or added to another to change or enhance its properties. In aviation maintenance, the term commonly refers to alloying elements added to a base metal, or to substances added to fuels, oils, and other fluids to improve performance characteristics.
Plain English
Something that has been put into a material or fluid to change how it behaves. For example, small amounts of other metals added to aluminum to make it stronger, or chemicals added to oil to help it last longer.
Context Anchor
Seen in aviation maintenance math, weight-and-balance calculations, measurements, and totals for parts, fuel, or equipment.
Derivation
From the Latin 'additio,' meaning 'a putting to' or 'something added.' In maintenance contexts, this everyday meaning carries directly over: it is literally what has been added to the base material.
Why Pilots Care
Accurate addition matters whenever separate amounts must be totaled, such as equipment weight, fuel amount, or maintenance measurements. A small arithmetic error can lead to a wrong final number.
Intuition Check
Do not read addition here as simply “installing something extra.” In this handbook context, addition means the math action of combining amounts to find a total.
Example Sentence 1
The strength of this aluminum alloy comes from the addition of small amounts of copper and magnesium.
Example Sentence 2
Careful addition of the fuel and oil amounts confirmed the aircraft remained within limits.