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| Symbol | Definition |
|---|---|
| ≡ | exactly equal |
| ≈ | approximately equal to |
| = | equal to |
| digits | indicates that digits repeat infinitely (e.g. 8.294 369 corresponds to 8.294 369 369 369 369 …) |
The femtometre (American spelling femtometer, symbol fm derived from the Danish and Norwegian word femten, "fifteen"+Ancient Greek: μέτρον, metrοn, "unit of measurement") is an SI unit of length equal to 10−15 metres, which means a quadrillionth of one. This distance can also be called a fermi and was so named in honour of physicist Enrico Fermi, as it is a typical length-scale of nuclear physics.
In typography, the stick, stickful, or stick of type was an inexact length based on the size of the various composing sticks used by newspaper editors to assemble pieces of moveable type. In English-language papers, it was roughly equal to 2 column inches or 100–150 words. In France, Spain, and Italy, sticks generally contained only between 1 and 4 lines of text each. A column was notionally equal to 10 sticks.