What is affix?

A word that sounds the same as another word

the beginning of a word

A word part added to the beginning or end of a word

The base part of a word

An affix: an additional element placed at the beginning or end of a root, stem, or word, or in the body of a word, to modify its meaning.

A word part added to the beginning or end of the word, is the answer to your question.

An affix is a word part added to the beginning or end of a word.

Affix is a term which includes prefixes (word parts added to the beginning of a word) and suffixes (word parts added to the end of a word). Affixes are used when you want to create a new word out of an old one. For example:

to imagine (verb) + - ation (suffix) = imagination (noun)

pre - (prefix) + determined (adjective) = predetermined (adjective)