The Function of the Prefix

In English grammar and morphology, a prefix is a letter or group of letters attached to the beginning of a word that partly indicates its meaning, including examples such as "anti-" to mean against, "co-" to mean with, "mis-" to mean wrong or bad, and "trans-" to mean across.

The most common prefixes in English are those that express negation, like "a-" in the word asexual, "in-" in the word incapable, and "un-" in the word unhappy —these negations immediately alter the meaning of the words the are added to, but some prefixes merely change the form.

Interestingly enough, the word prefix itself contains the prefix "pre-," which means before, and the root word fix, which means to fasten or place; thus the word itself means "to place before." Letter groups attached to the ends of words, conversely, are called suffixes, while both belong to the larger group of morphemes known as affixes. 

Prefixes are bound morphemes, which means they can't stand alone. Generally, if a group of letters is a prefix, it can't also be a word. However, prefixation, or the process of adding a prefix to a word, is a common way of forming new words in English.

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36 Common Prefixes in English

By Richard Nordquist

General Rules and Exceptions

Although there are several common prefixes in English, not all usage rules apply universally, at least in terms of definition. For instance, the prefix "sub-" can either mean "something below" the root word or that the root word is "below something."

James J. Hurford argues in "Grammer: A Student's Guide" that "there are many words in English which look as if they begin with a familiar prefix, but in which it is not clear what meaning to attach either to the prefix or to the remainder of the word, in order to arrive at the meaning of the whole word." Essentially, this means that sweeping rules about prefixes like "ex-" in exercise and excommunicate cannot be applied.

However, there are still some general rules that do apply to all prefixes, namely that they are typically set as part of the new word, with hyphens only appearing in the case of the base word starting with a capital letter or the same vowel that the prefix ends with. In "The Cambridge Guide to English Usage" by Pam Peters, though, the author does posit that "in well-established cases of this type, the hyphen becomes optional, as with cooperate."

Nano-, Dis-, Mis- and Other Oddities

Technology especially utilizes prefixes as our technological and computer worlds get smaller and smaller. Alex Boese notes in the 2008 Smithsonian article "Electrocybertronics," that "lately the prefix trend has been shrinking; during the 1980s, 'mini-' gave way to 'micro-,' which yielded to 'nano'" and that these units of measurement have since transcended their original meaning.

In a similar way, the prefixes "dis-" and "mis-" have come to slightly transcend their original intent. Still, James Kilpatrick claims in his 2007 article "To 'dis,' or Not to 'dis,'" that there are 152 "dis-" words and 161 "mis-" words in contemporary lexicography. However, many of these are never spoken like the word "misact," which starts the "mis- list," as he calls it.

The prefix "pre-" also has a bit of confusion in modern vernacular. George Carlin famously jokes about the everyday occurrence at the airport called "pre-boarding." According to the standard definition of the prefix, "preboarding" should mean before boarding, but as Carlin puts it "What does it mean to pre-board? Do you get on [a plane] before you get on?"