adj

• (of a device or system) In which the value of a data item (such as time) is represented by a continuous(ly) variable physical quantity that can be measured (such as the shadow of a sundial).
  "an analog watch"

noun

• (countable) Something that bears an analogy to something else.
• (countable, biology) An organ or structure that is similar in function to one in another kind of organism but is of dissimilar evolutionary origin.
  "See also: convergent evolution"
• (chemistry) A structural derivative of a parent compound that differs from it by only one or a few atoms or substituent groups; (usually, especially) such a molecule that retains most of the same chemical properties.