OldBoring wrote:What's the difference between vice and deputy in English?
I was really confused for a moment until I realised you meant "vice" as a prefix. ("Deputy" can be used alone as a title, but not "vice". That's one difference.)
I would say the difference it primarily lexical. That is, some titles take "vice" (e.g. "vice president", "vice principal"), some take "deputy" (e.g. "deputy sheriff"), and some take either (e.g. "vice/deputy director", "vice/deputy prime minister") depending on the institution. Arguably, "deputy" retains more the meaning of the original meaning of "person appointed to act on an officeholder's behalf" whereas "vice" simply denotes a rank below, but in practice I would say the choice is arbitrary and historical. Someone who is appointed to fulfill the duties of a vacant position without a formal job search, election, etc. would most commonly be called "interim".
And if that weren't confusing enough, a third element with much the same meaning is "lieutenant", as in "lieutenant colonel" or "lieutenant governor", which respectively denote an office just below that of "colonel", bzw. "governor". All of these titles originated with the idea of having someone ready to fill in if the person a step above (often the highest officeholder in that particular chain of command) was incapacitated.
"Richmond is a real scholar; Owen just learns languages because he can't bear not to know what other people are saying."--Margaret Lattimore on her two sons