The number of whole pictures per unit time, usually frames per second, f/s or Hz. Film usually runs at 24 frames per second (FPS).
A wide range of frame rates are used in modern media, typically from 23.976 to 120 frames per second. Framerates of thousands of frames per second are used by specialist cameras with applications in science, engineering, sport and wildlife video, where fast motion needs to be captured. Operation up to 120FPS is included in ITU-R BT.2020 recommendation for UHD.
UHD1 and UHD2 video provides higher resolution pictures, there is a strong argument that the shorter exposure times of higher frame rates is required to prevent motion blur. Higher frame rates may also lead to smoother motion portrayal. Some use of like the effect of “judder” at lower frame rates however, using it for dramatic effect or as part of a “film look”. Modern TV and electronic film standards give a wide range of choice.