Some common prefixes in the English language are "pre-," "un-," "re-" and "de-," according to Cambridge Dictionaries Online. Other common prefixes include "over-," "auto-," "anti-" and "mis-."
Prefixes are groups of letters that writers and speakers add to the beginnings of words to change their meanings, according to Cambridge Dictionaries Online. Prefixes can change base words to create opposites or to allow the words to describe time, manner or place. For example, when the prefix "un-" is added to the base word "able," the word "unable" is formed, which is the opposite of able. A prefix, such as "over-," allows a word to describe the manner in which something was done. For example, when "over-" is added to "cooked," the word becomes "overcooked," describing the manner in which something was cooked.
Sometimes, a prefix is added to a base word using a hyphen, such as in the word "super-intelligence," but sometimes the prefix and the base are not separated by a hyphen, as in the word "supermodel." There are no definite rules as to when a hyphen does and does not separate a prefix from a base word, so it is helpful to consult a dictionary when spelling out prefixed words.