Many English words are formed by taking basic words and adding combinations of prefixes and suffixes to them. A basic word to which affixes (prefixes and suffixes) are added is called a root word because it forms the basis of a new word. The root word is also a word in its own right. For example, the word lovely consists of the word love and the suffix -ly.
Lets look at the word unemployment
unemployment has a beginning (prefix), a middle (root word) and an ending (suffix).
un employ ment
Root word family examples
friend: friendly, friendship, unfriendly, friendless
faith: faithful, faithfully, unfaithful, unfaithfully