The concept of "undoing a registration" is widely used in my line of work. While most dictionaries define unregister as the proper verb for it, several widely used and highly considered sources also use the verb deregister. Do both verbs exist? Are they synonyms? Is there a slight difference in their meaning?

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    One possible advantage of using de- is to avoid ambiguity in the sentence "He was unregistered." If unregister is a verb, it's not clear whether this means he was taken off the registration list, or whether he was never on it. The sentence "He was deregistered" is unambiguous. Commented May 18, 2011 at 18:23

12 Answers 12


This is a question that used to plague me for ages, until I finally sat down and thought it through.

As a programmer, I see both used a lot, and often interchangeably. For me, I like to think of the question by beginning with another question: What is the 'not registered' state called?

Let's assume you're a programmer, but keep in mind this is applies anywhere. When you have a variable which represents some item that can be registered, what do you call the function to discover if it is registered? In all likelihood, you'll call it 'isRegistered()'. So in that sense, you make the problem into a boolean. i.e. is it registered, or is it NOT registered.

Then, from that logic, I believe your options simply become:

  • isRegistered() - false if the object is 'unregistered' - i.e. 'not registered' false == isRegistered().
  • registerSomething() - It has now moved from 'not registered' to 'registered'.
  • deregisterSomething() - It has now moved from 'registered' to 'not registered'. i.e. 'unregistered'.

This is why it's convention in programming to call an object that hasn't been 'initialised' as 'uninitialised', not 'deinitialised'. This implies it was never initialised to begin with, so its initial state is 'uninitialised'. If its initial state was called 'deinitialised' it would give the false impression that it was previously initialised.

The bottom line for me is that you should define a convention for its use in your particular context, and stick to it. The above convention is what I now use throughout my code.

Urgh... Here is all of that in a single line ;)

state=unregistered -> 'register' -> state=registered -> 'deregister' -> state=unregistered.

-- Shane

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    +1. I was just trying to solve the same identifier naming problem when I found this page. For some reason I can't help but draw a comparison in usage with the defrocking / unfrocking of vicars: there the two definitely are synonyms, as are defrocked and unfrocked. Here there is a distinction.
    – MZB
    Commented Sep 10, 2011 at 4:53
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    auth -> deauth. construct(or) -> destruct(or). I must convince myself to use deregister (even though the use of uninstall makes me doubt)
    – Daniel F
    Commented Aug 10, 2015 at 8:26
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    Yet, we use unsubscribe and not desubscribe. Sadly, while I agree with your rationale, natural languages are rather informal. Commented Sep 20, 2017 at 10:26
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    @David Rodríguez - dribeas - that's "unformal" if the subjected natural language has not been deformalized
    – Psyrus
    Commented Nov 5, 2017 at 12:18
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    It's just that “un-” is more versatile than “de-.” “un-” has two meanings for two different parts of speech: “(added to adjectives, participles, and their derivatives) denoting the absence of a quality or state; not” and “(added to verbs) denoting the reversal or cancellation of an action or state.” “de-,” on the other hand, is only added to non-participle verbs. “to unregister” and “to deregister” go (“un-/de-” + “to register”) and are synonyms; those verbs produce participles of the same meaning. Another “unregistered” is made from “un-” and a participle “registered.” Commented Nov 11, 2018 at 5:48

Here's a look at usage during the last 20 years:


As evidenced, unregister received a substantial boost shortly after the dot-com boom/bust of the late 90s, while deregister usage has been more or less the same throughout. It's worth noting that neither word is defined by any major dictionary, although some lesser dictionaries include the two. (Of course, placement in a dictionary does not mean a word is "real" or not - a word can exist anywhere - but it does indicate whether or not the word enjoys popular usage and if it has standardized spellings.)

Additionally, both the un- and de- prefixes can be defined as a reversal of action.

Despite the similarities, I'd go with popular usage and use unregister.

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    Both forms are still relatively uncommon, so we can't assume too much from a pretty small sample size. I imagine lots of people needed a word for the concept on account of the internet, spam, etc. This NGram suggeststhat 'non-standard' unregister got temporary currency from people almost randomly choosing without being actually familiar with either alternative. But deregister will win out when people realise they don't like unregistration. ngrams.googlelabs.com/… Commented May 18, 2011 at 16:24
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    @Fumble I agree about the sample size being small and arbitrary at best. But I don't feel the populist choice between two was entirely random: because of the significant usage unregister has in a technical context, the un- prefix has the benefit of a well-established precedent: undo, which is nearly ubiquitous as a means to reverse an action on hardware and software. It's entirely plausible that unregister gained traction by the use of this precedent. This is just supposition, however.
    – HaL
    Commented May 18, 2011 at 16:45
  • I quite agree about usage of unregister being influenced by a 'pre-existing' technical context. Which quite possibly would have made that form more common for labelling the appropriate link in web pages. But I still don't think speakers in general are going to accept unregistration over deregistration, so I'm still betting unregister will fade back over the next few years. Commented May 18, 2011 at 16:57
  • @Fumble I imagine time will tell. I prefer cancel myself.
    – HaL
    Commented May 18, 2011 at 17:03
  • Acceptance in a reputable dictionary is almost always considered an infallible test of wordness (at some point in time); usage panels will reject candidates they consider don't have enough currency. Of course, non-appearance in reputable dictionary A doesn't prove much, especially when dictionary B lists the word. Commented Feb 19, 2021 at 19:21

Generally speaking, the de- and un- prefixes have different usages.

Un- more usually negates an adjective: unkind, unfair, etc. On the other hand, de- is a verb prefix, that denotes the action of removing some thing or state.

Hence: unleaded petrol/gasoline (because lead doesn't occur in petrol until it's added) but decaffeinated coffee (because the caffeine has been taken out).

However, when an adjective is from a verb, usage often slips from this, and we end up with un- prefixing a new verb. So the adjective unregistered gives rise to the verb to unregister, although deregister would be more in line with convention.

By this convention, unregistered should mean not registered (whether through active deregistration or never having been registered in the first place) and there should be no verb to unregister. Deregistered should mean actively removed from the register.

(The verb to undo is I think the most notable exception to the conventional norm.)

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    Yes. Compare "unconnected" and "disconnected." You can only be "disconnected" if you were previously "connected." If you were never "connected," then you remain "unconnected."
    – Eli Skolas
    Commented Jul 12, 2016 at 9:17

I've checked the OALD, the NOAD and the OED and, surprisingly for me, none has "unregister".

The only similar entry is unregistered which means "not recorded".

But the OED (only this one) has deregister and gives this entry:

Deregister, v. (diːˈrɛdʒɪstə(r))
[de- + register]

trans. To remove from a register. Hence ˌderegiˈstration.

It appears also here (it's an OED online, considering the credits given), while unregister, again, is not available. I can understand that some old Dictionary doesn't have unregister, but I can't understand why the Oxford Advanced Learner's Dictionary doesn't have any entry considering it's online and therefore has more opportunities to be revised and updated. Not to mention that I've seen unregister before, because it doesn't sound new to me.

  • This is the answer I was looking for. To remove (transitive) from a register is to deregister and, once removed, the status of the object is unregistered (passive).
    – Konchog
    Commented Apr 6, 2021 at 9:06

I found this.

Deregister: to unregister


So, they seem like synonyms to me.

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    And yet, other answers seem to distinguish between them as un- (not registered now) and de- (was registered before, but not any more).
    – ANeves
    Commented Feb 26, 2018 at 21:08
  • After reading this answer I would rather say Deregister: to make something unregistered.
    – Qwerty
    Commented Oct 25, 2021 at 9:08

I would suggest that unregistering is the undoing of some registration that should never have taken place, e.g. a license that should never have been issued, whereas deregistering is the removal of some registration that is, perhaps, no longer valid. In the latter case, there is an element that it was once a valid registration but its status has changed. The former case suggests there should be no record the registration ever existed.

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    This is similar to the word "connect." When you are not connected, you are "unconnected." When you were once connected but the connection has been removed, you have now been "disconnected."
    – Eli Skolas
    Commented Jul 12, 2016 at 9:14

"Deregister" carries more of an active connotation than "unregister". For example, while the "unregistering" might involve removing your name from the guest list for a conference, "deregistering" would also include cancellation of hotel reservations, travel plans, etc.

  • Isn't it subjective? Commented May 18, 2011 at 20:18
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    If so, it may be suggested by the way that "de-" seems to always imply reversal of an action, while "un-" can simply mean "not". I hope I am being "unassuming" and not "defensive" here.
    – JeffSahol
    Commented May 18, 2011 at 20:42
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    I did not vote your answer down, so please don't feel bad about it. My knowledge of the English language is too limited to either believe you or prove you wrong. (By the way, I'm pretty sure that the "de" in "defensive" is no privative prefix) Commented May 18, 2011 at 21:08
  • Yes, I was stretching for a weak pun there before I had to leave for home. Great question, by the way.
    – JeffSahol
    Commented May 18, 2011 at 23:47

Shane's got it right, deregister is the verb to move someone from state=registered, to state=unregistered, IMHO.

With respect to defrocking/unfrocking, I think vicars are 'defrocked' by their superiors after they've been caught 'unfrocking' with the wrong people at the wrong time.

This leads to another possible distinction- One 'unregisters' themselves, and 'deregisters' others. If I am registered for notification, I can 'unregister' myself, but the notification service could deregister me if communications were lost.


In OALD, only unregistered is found because this word is always used in passive voice. As a reference dictionary, OALD will never mention this word without -d.

And actually, grammatically, unregistered is more likely an adjective because it is a past participle, and a past participle can be often used as an adjective.

  • prefix un- means undo(ctrl + z) of something.
    • Examples: unlike, uncover, unregister, unsubscribe,
  • prefix de- means do reverse of something
    • Examples: demonetization, deactivate, decompile
  • This question was marked as answered six years ago and your answer doesn't really add anything or answer the question. I'd consider deleting it. Commented Oct 6, 2018 at 8:36

I believe the most popular (and accepted) answer starts going in the right direction (thinking of what the act of "deregistering" does and the state transition), but then wrongly concludes "deregister" is redundant because the "unregistered" state is the same as what happens after "deregistering".

If you really think about the state transition after a "deregistering" action though, it is not at all the same as not having been registered in the first place. For example, consider a stock that has been "delisted" from an exchange. Depending on how it has been delisted, there may be certain actions an investor holding the stock could still do on the exchange, but of course, an unlisted stock cannot have any actions taken on it (other than to list it!).

As another set of examples, consider a licensed professional that has been "delicensed". It's interesting to note many professions have special terms for this state, e.g. a lawyer is disbarred, a priest is defrocked (there is an actual verb "frocked" but seems to have fallen into disuse). A medical doctor does seem to be "delicensed" but commonly one sees "disbar" also being used nowadays.

The point of these examples is to show that this state of being "deregistered" is hugely significant in a variety of business domains. One would not simply keep track of a boolean (true/false) but instead keep track of other variables. As the accepted answer even notes, an "uninitialized" variable means something different than a "deinitialized" variable. The former is just the default but the latter is on purpose and may signify critical business logic. It's unfortunate, and the cause of many bugs, that developers don't actually distinguish between the two cases when they should.


Unregister means the item or person does not appear on the list because they were never on the list.

De-register means the item or person was initially listed, but has been removed and is no longer on the list.

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