Definition
A numerical expression representing a part of a whole, written as one number divided by another (for example, 1/2, 3/8, or 7/16). The top number (numerator) shows how many parts are taken; the bottom number (denominator) shows how many equal parts the whole is divided into.
Plain English
A way of writing part of something using two numbers stacked together. The bottom number tells you how many pieces the whole was cut into, and the top number tells you how many of those pieces you have.
Context Anchor
Seen in maintenance manuals, measurement conversions, part dimensions, and shop math used during inspection or repair work.
Derivation
From the Latin fractio, meaning 'a breaking.' A fraction is literally a 'broken piece' of a whole — which fits how it's used: showing how a whole has been broken into equal parts.
Why Pilots Care
Aviation maintenance uses fractional measurements constantly — bolt sizes, drill bits, sheet metal thicknesses, torque values. Misreading a fraction (3/8 vs 5/16) can mean the wrong tool, the wrong part, or an out-of-tolerance repair.
Intuition Check
Do not think of a fraction as only a school math symbol. In maintenance, a fraction is often an exact measurement, such as 3/16 inch, that must be read and used correctly.
Example Sentence 1
The technician selected a 7/16 inch wrench, reading the fraction stamped on the handle.
Example Sentence 2
Convert the decimal reading to a fraction before comparing it to the tolerance.