analog

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Something that bears an analogy to something else; something that is comparable.
• noun Biology An organ or structure that is similar in function to one in another kind of organism but is of dissimilar evolutionary origin.
• noun Chemistry A structural derivative of a parent compound that often differs from it by a single element.
• adjective Of, relating to, or being a device in which data or a signal is represented by continuously variable, measurable, physical quantities, such as length, width, voltage, or pressure.

from The Century Dictionary.

• noun A simplified spelling of analogue.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective of a device or system in which the value of a data item (such as time) is represented by a continuously variable physical quantity that can be measured (such as the shadow of a sundial)
• noun countable something that bears an analogy to something else
• noun countable, biology an organ or structure that is similar in function to one in another kind of organism but is of dissimilar evolutionary origin
• noun chemistry a structural derivative of a parent compound that often differs from it by a single element

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• adjective of a circuit or device having an output that is proportional to the input
• noun something having the property of being analogous to something else