In the English language, a prefix or suffix can be added to a root word to modify its meaning. A prefix comes before the root word, and a suffix comes after. The prefix and suffix are known as affixes, or additions to a word, and are differentiated by their placement against a word.
Common prefixes include un-, dis-, mal-, non-, mid-, and mini-, while common suffixes are –ed, -s, -es, -ing. Suffixes often indicate the tense or number of a word, but can also be used to indicate the part of speech. For example, adding –ly to the end of a word often indicates that word is an adverb. The prefix and the suffix can take on different meanings depending on the root word it precedes or succeeds, and therefore they are reliant on the root word and cannot stand alone.
In many cases, adding a prefix or suffix to a word changes the meaning of that word entirely. For example, the word "latch" means to secure or fasten. But by adding the prefix un- to the root word to create "unlatch," the meaning has been changed to mean release or let free. In this case, the addition of a prefix has made the word mean the opposite of the root word. Taking that same root word and adding the suffix –ed to create "latched" changes the tense of the word. While the root word takes place in the present tense, by adding –ed the action indicated by the word now has taken place in the past.
The roles of the prefix and the suffix have been embellished over the course of centuries, and it is not uncommon to see new words being formed by the addition of one or both. For example, television personality Stephen Colbert recently coined the term, "truthiness" by adding a suffix to the word "truth" to indicate an idea or concept that has elements of truth to it but is not necessarily the truth. While the word is somewhat nonsensical, the addition of the –ness suffix made the word catchy and many linguists applauded the new creation.