Definition: The hertz is the derived unit used for periodic phenomena, like frequency.

Source: SI Brochure 9th Ed. 2019, p 137

Status: Valid

Notes

The hertz is the SI coherent derived unit for frequency.

The hertz shall only be used for periodic phenomena.

The SI unit of angular velocity and angular frequency is radian per second.

It is particularly important to carefully distinguish frequencies from angular frequencies, because by definition their numerical values differ by a factor of 2π.