The word discrete comes from the Latin word discretus which means separate. It is used with different meanings in different contexts:

• In perception, a discrete entity is something that can be perceived individually and not as connected to, or part of something else.
• In mathematics, a discrete set is a countable set (except in topology, see below). The mathematical study of discrete sets is the area of inquiry for discrete mathematics, but is also important for combinatorics, probability theory, and statistical theory.
• In topology, a branch of mathematics, a discrete space is a topological space in which all sets are open.
• In discrete mathematics and in theoretical computer science, the abstract world is usually modeled as a discrete space with discrete time.
• In electrical engineering, discrete means having separate electronic components, such as individual resistors and inductors. This is the opposite of integrated circuitry.
• In audio engineering, discrete means having separate and independent channels of audio, as opposed to matrixed stereo or quadrophonic, or other multi-channel sound.
• In reference to signals, dynamic systems, or control theory, discrete often means the same thing as digital.
• In music, a discrete pitch is one with a steady frequency, rather than an indiscrete gliding, glissando or portamento, pitch.

Discrete is not the same thing as discreet.