The difference between levels for turn-on and turn-off operation in a control system.

1. The differential of a real-valued function f (x ), where x is a vector, evaluated at a given vector c, is the linear, real-valued function whose graph is the tangent hyperplane to the graph of f (x ) at x =c; if x is a real number, the usual notation is df= f'(c )dx.

2. See <<total differential>>

Any arrangement of gears forming an epicyclic train in which the angular speed of one shaft is proportional to the sum or difference of the angular speeds of two other gears which lie on the same axis; allows one shaft to revolve faster than the other, the speed of the main driving member being equal to the algebraic mean of the speeds of the two shafts. Also known as differential gear.