Dead zone
A region near an analog stick's centre where small movements are ignored, so wear and skew don't drive the character when the player lets go.
An analog stick rarely rests at exactly zero — springs and potentiometers add a little noise, and over time "stick drift" that sticks in one direction. A dead zone zeroes everything inside a threshold so that rest really means still. The price is precision: make the zone too large and the first few degrees of movement feel dead and the control blunt.
The simplest version clips each axis on its own (axial), which leaves a square dead patch and makes clean diagonals hard; a radial dead zone measures the stick's distance from the centre instead and behaves the same in every direction. The detail belongs to the same family of invisible game-feel tricks as coyote time and input buffering — barely noticeable alone, decisive together.