Final answer:
Aver is a synonym for certain, and weary is its antonym in English.
Step-by-step explanation:
The word 'aver' is a synonym for 'certain' while the word 'weary' is an antonym of 'certain'.
In English, synonyms are words that have a similar meaning, while antonyms are words that have opposite meanings.
For example, if someone is 'certain' about something, they have no doubt or uncertainty. On the other hand, if someone is 'weary', they are tired or exhausted.