Final answer:
A synonym is a word with a similar meaning, while an antonym is a word with an opposite meaning.
Step-by-step explanation:
In English, a synonym is a word that has a similar meaning to another word. For example, a synonym for 'absence' could be 'lack' or 'nonexistence'. On the other hand, an antonym is a word that has the opposite meaning to another word. For 'success', an antonym could be 'failure' or 'defeat'.