A suffix is a letter or group of letters added to the end of a word. Knowing what a suffix means can help us to understand new words.
For example, the suffix -er can mean a person who does something.
If you teach someone you are a teacher.
If the word ends in -e then we just add -r.
manage / manager
If the word ends in -y we have to change it to 'i' before we add the suffix.
qualify / qualifier