1. Something that is analogous or similar to something else
2. An organ or part similar in function to an organ or part of another animal or plant but different in structure and origin
3 usually analog; a chemical compound that is structurally similar to another but differs slightly in composition (as in the replacement of one atom by an atom of a different element or in the presence of a particular functional group)
4. A food product made by combining a less expensive food (as soybeans or whitefish) with additives to give the appearance and taste of a more expensive food (as beef or crab)

Pertaining to or being a device or signal that is continuously varying in strength or quantity, such as voltage or audio, rather than based on discrete units, such as the binary digits 1 and 0. A lighting dimmer switch is an analog device because it is not based on absolute settings. Compare digital (definition 2).
(of a quantity or device) Changing continuously; by contrast a digital quantity or device varies in series a of distinct steps. For example, an analog clock measures time by means of a continuous movement of hands around a dial, whereas a digital clock measures time with a numerical display that changes in a series of discrete steps.

Most computers are digital devices. Therefore, any signals and data from an analog device must be passed through a suitable analog-to-digital converter before they can be received and processed by computer. Similarly, output signals from digital computers must be passed through a digital-to-analog converter before they can be received by an analog device.