# Definition:Angle/Unit/Second

## Definition

The second (of arc) is a measurement of plane angles, symbolized by $''$.

$1''$ is defined as $\dfrac 1 {60}$ of a minute of arc, or $\dfrac 1 {3600}$ of a degree of arc.

## Historical Note

The division of the degrees into $60$ and $3600$ subdivisions originates from the Babylonians, who used a sexagesimal (base $60$) system for the purposes of mathematics and astronomy.

## Linguistic Note

The word second, in the context of the measurement of time and of angle, derives from the fact that it was originally specified as a second minute part of an hour or of a degree of arc.

The minute had already been defined as a minute part of an hour.

The use of the word second in English, in this specific context, started near the end of the $16$th century.