35 Common Prefixes in English

If you were a prefix, you could change the same word in different ways.You could make a cycle a unicycle, a bicycle, or a tricycle.
_{(Marcie Aboff and Sara Gray, "If You Were a Prefix." Picture Window Books, 2008)}

A prefix is a letter or a group of letters attached to the beginning of a word (or word root) that partly indicates its meaning. For example, the word prefix itself begins with the prefix pre-, which generally means "before" or "in front of." (By contrast, a letter or group of letters attaching to the end of a word is called a suffix.) 

Many of today's English words contain prefixes from Greek or Latin. Understanding the meanings of the most common prefixes can help us deduce the definition of new words that we run across in our reading, especially knowing that they can make a word mean its opposite, such as the difference between possible and impossible.
Still, we do need to be careful. The same prefix may be ​spelled in more than one way (pre- and pro-, for instance), and some prefixes (such as in-) have more than one meaning (in this case, "not" or "without" versus "in" or "into"). Even so, being able to recognize prefixes can help us build our vocabularies. 

Rules vary as to when a word should have a hyphen separating it from its prefix. Go by the dictionary if you are unsure. If you are writing a paper for a class and a particular style guide is used, such as MLA, the Chicago Manual of Style, or APA, the stylebook may have a hyphenation guide or a preferred dictionary to follow for which words to hyphenate and which to close up. If a prefix is attached to a proper noun, you generally hyphenate, such as pre-World War II or anti-American. 

The following table defines and illustrates 35 common prefixes.