An affix (prefix, suffix, infix, etc.) is a group of letters added to a word to modify the meaning or create a new word.
For example, the suffix -or can mean a person who does a particular action. Hence: actor, editor, inventor, visitor, etc. The prefix biblio- means book, from which we get words such as bibliography and bibliophile.
The online Dictionary of Affixes contains many affixes and examples. It has recently been updated.
Source: Sentence First