An antonym is the complete opposite of something.. black and white are probably the best known examples. The great thing is that antonym is the first global relation type and in the way it is set up, the antonym is true on a concept level. This means that it does not allow for cultural differences in the appreciation of such a relation.
I wonder how many antonyms will prove to be problematic because of cultural differences. The good news is that we are now able to have global relation types in OmegaWiki. We will have to be REALLY careful what relation types we will include. The "is a" relation is not going to be part of it because that is what makes something a class member.
With the global and the class based relation types we only need the collection based relation types to get our full functionality :)