About Frequency
Frequency is the number of cycles or oscillations per unit time. The hertz (Hz) is the SI unit, equal to one cycle per second.
Radians per second (rad/s) is the angular frequency — related to Hz by ω = 2π × f. RPM (revolutions per minute) is common in mechanical applications.
Pro Tips
Human hearing range is roughly 20 Hz to 20 kHz. Wi-Fi typically operates at 2.4 GHz or 5 GHz.
Period (seconds) is the inverse of frequency: T = 1/f. A 60 Hz power grid cycles every ~16.7 ms.