What are the differences between an "opposite" and "antonym"?
For all practical purposes, the two are equivalent when used to describe words*.
Etymologically, "opposite" came to us from Latin, via French, while "antonym" came from Greek, also via French.
Latin: oppositus, or "set against"
Greek: ant- + onuma, or "against a name"
*as mentioned in my comment below, if the context is not limited to the description of words, then an antonym is a very specific type of opposite -- an opposite of another word.
As of now Wikipedia is considering both the same.
That is, if you search there for
Antonym you will reach at a page titled
But then again, at the top of the article, Wikipedia notes that
This article needs attention from an expert on the subject. See the talk page for details. WikiProject Linguistics or the Linguistics Portal may be able to help recruit an expert. (November 2008)
And if you go to the talk page, you will get plenty of reasons why Antonym should never have been moved to Opposite (semantics)
And that article argues that
Antonym is different from
Opposite with very valid points.
A good excerpt will be
"Antonym" is very much a definitive linguistic term unlike the imprecise "Opposite" which is not saved by the pretentious "(semantics)" tag. "Opposite" can be anything, "antonym" can be only one thing.