The Most Common Prefixes and Their Meanings

Posted by Alison on 10/17/16 6:00 PM

grammar.pngThe English language comprises a plethora of words that can change meanings with the addition of a prefix or a suffix. For example, the prefix re signifies that the base word to which it attaches is happening again, as in "do" and "redo". In theory, one could add re an infinite number of times to the front of a word, and the effect would continue to do the same thing; the word's function would be repeated however many times the prefix re appears. The fact that such a pattern exists in English recalls an aspect of the language (there it is again, re in recall to call to mind again) that dates back to its origins. As much as English is a language full of exceptions to the rules, it also presents patterns that, when understood, can shed light on how and why we use the words that form the English language.

Learning Negative Prefixes

One such pattern is the addition of a negative prefix before a word, to change the word's meaning to its opposite or counterpart. A prefix is a part of a word that precedes the stem or base word. In linguistic terms, prefixes are part of the broader category of affixes, which are morphemes (parts of a word) that attach to a base to form a new word. For example, un has the effect of undoing what its base word conveys. Do and undo, fold and unfold, known and unknown, familiar and unfamiliar. If a non-native English speaker knows this rule, then in theory he or she can understand that a word would become its opposite with the addition of un at the beginning, even if the speaker does not know the meaning of the base word itself.

English is cool that way. But it is also not as simple as this one example may suggest. Why is it undo and not non-do? Or misunderstood instead of disunderstood? This post will reveal some of the patterns and curiosities of the many negative prefixes in English and when and why to use each one.

1. Understanding Un-

Apparently the prefix un has existed longer than the prefix dis. Both have almost identical functions, but their origins explain their potentially different uses. The prefix un results from a spelling change from the Old English on and has the effect of reversing or negating the base word to which it attaches. Simply put, un means not. Words such as ungrateful, unhappy, unfinished, unsettled, and undo, exemplify this prefix's function to represent a lack or reversal of the base word it precedes.

2. Dis- is a little different

While un comes from Old English, dis emerged instead during the Middle English period, deriving from Latin and French des. In Latin, dis meant "away from" or "apart". Dis also derives from the similar bis, of Greek origins, meaning two, or divided in two. From this, words like disjoin, disconnect, and discontent make sense because they mean the opposite of their bases: disjoin is to take apart (to separate or not join), disconnect is to become no longer connected, and discontent means not content. This logic works even with words that are less intuitive, like disclose, meaning to reveal previously unknown information. When we look at the word's breakdown, we see dis + close from French des (away from) + Latin claudere (to close). Together this means to do the opposite of close, as in to open up a secret.

Other common words that use dis as a prefix include disappear, disqualify, dishonest, disagree, disadvantaged, disability, and dislike.

3. Other dys-functional prefixes

What about that closely related variant of dis, spelled dys? What is really the difference? It turns out that dys has different origins than dis, which accounts for a difference in meaning. Dys comes from the Greek root for "bad" or "abnormal", whereas dis derives from the Latin prefix meaning "away from" or "opposite", as explained above. Therefore, dysfunctional does not just mean not functional. It means functioning in a bad way. The majority of words that use dys as a prefix are medical or scientific terms, such as dyslexia (having an abnormal ability to read) or dystopia (an imaginary place in which bad circumstances prevail over good).

4. Non- is noncommittal

While un just means not, its relation non can have a subtly diverse effect. Non, meaning not, tends to function as a neutralizing or absolute not, rather than assigning an actively negative connotation. For example, uncommitted might refer to a lack of willingness or ability to devote oneself to a cause. To call someone uncommitted to a job is not a compliment. In slight contrast, noncommittal simply means not committing or not making a decision either way. It is not expressly negative in meaning.

One of the most often-made mistakes in day-to-day language use is the confusion between disinterested and uninterested. These are not interchangeable, as much as people might want or believe them to be. Uninterested means decidedly not interested. If I am uninterested in going to the movies, I do not want to go to the movies. Or if you are telling me about your broken toaster, and I tell you that I am uninterested, it means that what you are telling me is not interesting. It is instead, unfortunately, boring me.

Disinterested means detached from an interest in any particular relevant topic. It means having no bias or leaning in any one direction. Judges should be disinterested in their rulings, so that they are not being unfairly persuaded or swayed by partialities. When you are boring me with your toaster story, it is incorrect to say I am disinterested. I am actually uninterested. I do not want to hear it.

5. Mis-understandings and mis-uses

Mis is another negative prefix. It comes from Old English and is of Germanic origin, stemming from the Proto-Germanic "missa", which meant changed from or astray. In this way, mis has the effect of conveying error to the words in which it is used. For example, to misuse a word is to use the word incorrectly, in a way that is mistaken. Mistaken means taken badly, in a way that is not meant to be. Misunderstand is to understand something as being changed from its intended meaning, or to understand something differently (wrongly) from what it is supposed to mean.

6. In- contrast

In also derives from Latin and comes in several forms. When placed in front of a word, in has the same effect of negation, but it only attaches to Latin derivatives. Depending on the consonant that follows, the prefix in may become il-, im-, or il- through a phonetic process called assimilation. Thus we have incorrect, impenetrable, illiterate, and irrational.

7. And -in some cases...

In- can mean its direct opposite. For example, illuminate means to make more luminous, as opposed to taking away light. There are also words like inflammable and flammable, which have exactly the same meaning – able to catch on fire – despite the addition of a typically negative prefix at the beginning of one and no prefix at the beginning of the other. This is one of those exceptions to the rules that make English easy to misunderstand but also fun to discover.

For some more entertaining examples of words and phrases that mean their exact opposite, enjoy this post from

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