What does the prefix de- mean?
De- shows that an action is undone or reversed. It works like the "undo" button: what was done goes back. You will meet it with verbs about switching things off, reversing a process or getting rid of something.
ESEN
Prefix · reversal / removal
de-
Reverses or removes an action or condition: defrost, decode, deactivate, debug, dehydrate.
Basic
Written by Bryan López, English teacher · Updated
De- also means removing or reducing
Besides reversing, de- can mean removing something or making it smaller. In these cases there is not always a previous action being undone: something is simply taken away, like water, value or trees. If you see a verb with de-, ask yourself: is something being undone, or is something being taken from it? That is almost always enough to guess the meaning.
How it is used
Attaches to verbs, nouns, and adjectives with no spelling change:
- de- + verb (reversal)frost → defrostcode → decodeactivate → deactivatehydrate → dehydrate
- de- + verb/noun (removal)forest → deforestvalue → devaluebug → debugrail → derail
Pronunciation: /diː/ in everyday words (defrost, debug) and /dɪ/ in more formal words (devalue, dehydrate). Both are correct.
How it is pronounced
de-/diː/ or /dɪ/
Tap the button to hear how the prefix sounds. Each word in the table has its own audio.
Examples
Root word
With de-
In a phrase
- frostdefrostRemember to defrost the chicken before cooking it tonight.
- codedecodeAnalysts worked overnight to decode the encrypted message.
- activatedeactivateYou can deactivate your account anytime from settings.
- hydratedehydrateRunners risk getting dehydrated if they skip water breaks.
- forestdeforestThe region was heavily deforested to make room for farmland.
- bugdebugShe spent the afternoon debugging the new checkout module.
- railderailA sudden disagreement nearly derailed the entire negotiation.
Common mistakes
de- and dis- are always interchangeable
de- reverses or removes; dis- negates or separates
"Deactivate" reverses a previous activation; "disable" removes the ability to function. The difference is subtle but real in careful usage.
debug = add bugs to the code
debug = remove bugs (errors) from the code
De- in "debug" signals removal. It is a technical programming term meaning to find and fix errors in code.
A trick to remember it
Picture an "undo" button: de- reverses an action, like hitting Ctrl+Z on a verb. defrost, decode.
Practise what you learned
Exercise 1 · Form the word
Exercise 2 · Pick the right one
"Make sure to ___ the chicken in the fridge the night before you plan to cook it."
Exercise 3 · Pick the right one
What is the main difference between "de-" and "dis-"?
Frequently asked questions
What does the prefix de- mean in English?
The prefix de- reverses or removes an action or condition: defrost, decode, deactivate, debug, dehydrate.
How do you pronounce de-?
The prefix de- is pronounced /diː/ or /dɪ/. For example, "defrost".
Can you give an example of a word with de-?
"frost" becomes "defrost". It is a typical example of the de- prefix.
Other useful prefixes
Learn every English prefix
un-, re-, pre-, dis-, over-, in-... every beginning you need to unlock thousands of English words at once.