What does analogy mean?
The definition of analogy
A*nal”o*gy, n.; pl. Analogies.
Etym: [L. analogia, Gr. analogie. See Analogous.]

1 A resemblance of relations; an agreement or likeness between things in some circumstances or effects, when the things are otherwise entirely different. Thus, learning enlightens the mind, because it is to the mind what light is to the eye, enabling it to discover things before hidden.

Note: Followed by between, to, or with; as, there is an analogy between these objects, or one thing has an analogy to or with another.
Note: Analogy is very commonly used to denote similarity or essential resemblance; but its specific meaning is a similarity of relations, and in this consists the difference between the argument from example and that from analogy. In the former, we argue from the mere similarity of two things; in the latter, from the similarity of their relations. Karslake.

2 (Biol.)
A relation or correspondence in function, between organs or parts which are decidedly different.
3 (Geom.)
Proportion; equality of ratios.
4 (Gram.)
Conformity of words to the genius, structure, or general rules of a language; similarity of origin, inflection, or principle of pronunciation, and the like, as opposed to pl. analogies. Johnson.