Difference between antonyms and antithesis?
Antonym = A word opposite in meaning with another
Antithesis = A person or thing that is the direct opposite of somebody or something else
Antonym's relate to specific words, while antithesis relates to things and people. For example:
The antonym of happy is sad, while the antithesis of fire is water.
The antonym of good is bad, while the antithesis of the sky is the ground.
The antonym of traditional is contemporary, while the antithesis of Harry Potter is Voldemort
Notice that the words I use for antonyms are usually abstract concepts, things that you can't really visualize by themselves in reality, while the things and people I use for antithesis can be visualized. Essentially, the difference between antonym and antithesis is that an antonym is a word having the exact opposite definition of another, while antithesis is being the exact opposite, flat out.
I hope that helped!