2.NounSomething that bears an analogy to something else.
3.NounAn 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"
4.NounAlternative spelling of analog (“A structural derivative of a parent compound that differs from it by only one or a few atoms or substituent groups; such a molecule that retains most of the same chemical properties.”)