an·a·log or an·a·logue 
(ănə-lôg′, -lŏg′)
(ănə-lôg′, -lŏg′)n.
1. Something that bears an analogy to something else; something that is comparable: "Titan, Saturn's giant moon ... seems like an analog of the environment of Earth on the eve of life" (David Grindspoon).
2. Biology An organ or structure that is similar in function to one in another kind of organism but is of dissimilar evolutionary origin.
3. Chemistry A structural derivative of a parent compound that often differs from it by a single element.
adj.
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.
[French analogue, analogous, analog, from Medieval Latin analogus, from Greek analogos, proportionate; see ANALOGOUS.]