# Definition:Imperial/Length/Inch

## Definition

The inch is an imperial unit of length.

 $\ds$  $\ds 1$ inch $\ds$ $=$ $\ds 2 \cdotp 54$ centimetres $\ds$ $=$ $\ds 0 \cdotp 0254$ metres

This definition is exact, and is how the imperial unit of length is defined.

## Linguistic Note

The word inch derives ultimately from the same root as ounce, that is, from the Latin word uncia, meaning $\dfrac 1 {12}$ part.

In this context, the inch is of course the $\dfrac 1 {12}$ part of a foot.

From the same root, the uncial letters of a mediaeval manuscript are letters which are an inch high.

Despite the gradual migration to the metric system, the word inch still lives on as a rhetorical flourish for a small distance, for example:

Slowly and steadily they inched forward ...
Give him an inch and he'll take a mile.