A suffix is a small group of letters (an element) which is attached to the end of a word in order to modify (alter) its meaning. For example:
Incidentally, if the element is added to the front of a word, it is called a prefix. Prefixes and suffixes are not normally words in themselves. Finally, unlike prefixes, suffixes tell you what part of speech a word is, for example:
This 11-plus English quiz will give you some practice in identifying what part of speech a particular word is. Don't forget: each part of speech tells you how the word is used.