An arcsecond, also called a $\textit{second of arc}$, is a unit of angle equal to $1/60$ arcminutes, or 1/1296000 of a turn. The recommended symbol for the arcsecond in the is the $\textit{double prime}$ ($''$). In combination with prefixes, the symbol $as$ has also become common, like in astronomy, where very small angles are stated in milliarcseconds ($mas$).
Arcsecond