An Etymological Dictionary of Astronomy and Astrophysics

1. A similarity or comparability between two things.
   

2. Math.: A general similarity between two problems or methods. Analogy is used to infer new theorems from existing ones. Hypotheses based on analogy must still be proved.
   

3. Logic: A form of reasoning which asserts that if two or more entities are similar in one or more respects, then they would be similar in other respects.
   

4. Biology: An analogous relationship.
   

5. Linguistics: The process by which a word or form is either created or changed according to existing patterns in the language.

See also: M.E., from O.Fr. analogie or directly from L. analogia, from Gk. analogia “proportion,” from → ana- “upon, according to” + logos “ratio; word, speech, reckoning,” → -logy.