"unorthodox" vs "heterodox"

What's the difference between "unorthodox" and "heterodox"?

The dictionary I use roughly states that "heterodox" means "not orthodox", and "unorthodox" means well, "not orthodox".

Are they perfect synonyms?

Solution 1:

The term unorthodox is used of things which do not adhere to “orthodoxy” but are not necessarily in opposition to it: “An unorthodox solution to the problem”. But I’ve only ever seen the term heterodox used for matters which oppose orthodoxy: “A heterodox sect”.

Also, as indicated by the examples I’ve given, unorthodox is usually contrasted to a figurative orthodoxy, a norm; heterodox is most commonly used in contrast to a literal orthodox theology.

Solution 2:

To be UNorthodox is to actively go against orthodoxy. To be "heterodox" is to be "different" from orthodoxy. But this "difference" could be passive, rather than active.