The inverse second or reciprocal second (s−1), also called per second, is a unit defined as the multiplicative inverse of the second (a unit of time).
It is applicable for physical quantities of dimension reciprocal time, such as frequency and strain rate.
It is dimensionally equivalent to: However, the special names and symbols above for s−1 are recommend for clarity.
[a][b] Reciprocal second should not be confused with radian per second (rad⋅s−1), the SI unit for angular frequency and angular velocity.
The inverse minute or reciprocal minute (min−1), also called per minute, is 60−1 s−1, as 1 min = 60 s; it is used in quantities of type "counts per minute", such as: Inverse square second (s−2) is involved in the units of linear acceleration, angular acceleration, and rotational acceleration.