In my current project we are writing a program to convert a newer protocol to an older one.

These conversion programs are being referred to as adapters, but the team cannot agree which spelling to use: adapter or adaptor.

I personally plump for adapter, as adaptor sounds like its a person (like actor, realtor, etc.) rather than a device.

Is there a case for using one rather than the other?


5 Answers 5


Both are commonly used and listed in dictionaries, but adapter (with an e) is usually listed as the more common - see, for example, Merriam Webster or the Cambridge dictionary. It's not a strong basis for choosing one over the other, but it might be enough to settle the matter in your case :).

  • Thanks for all the help. I think Billares links sent me off in the right direction! Apr 25, 2011 at 10:35
  • 1
    Really? I have never, ever seen "adapter".
    – Marcin
    Apr 25, 2011 at 13:21
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    @Marcin: Yes, really :) If you don't trust the dictionary sources I mentioned (one UK, one US), try picking a website (e.g. BBC or CNN news, or your local Amazon site) and searching for both spellings... in all the searches I've tried, adapter dominates.
    – psmears
    Apr 25, 2011 at 14:23
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    Clearly, it is not uncommon, but it's still a new one on me.
    – Marcin
    Apr 25, 2011 at 15:12
  • Interesting. ASL has an sign for an agent (e.g. learner/student, teacher) which also applies to inanimate objects like printers (PRINT+AGENT). Dec 17, 2012 at 21:28

I would tend to suggest in a situation like this where both spellings are considered acceptable to use the spelling that is most broadly accepted in the particular field you are working in. In this case, the leading example of usage of the word "adapter" is the description of the kind of system you are writing in Design Patterns: Elements of Reusable Object-Oriented Software by Gamma, Helms, Johnson and Vlissides, commonly referred to as "Gang of Four" or "GoF". This book (which is among the most widely-read books on software design there are) uses the -er spelling, so I would suggest that anybody else working on software adapters should also use that spelling.


The British newspaper The Guardian, for instance, makes a distinction between adaptor vs. adapter in its internal style guide, namely, use adaptor when referring to devices and adapter when referring to people.


Here's a good article on the subject... essentially, there is no 'correct' answer to this question.

Incidentally, some would argue quite the opposite in regards to either form referring to people or objects. There are (not literally of course) endless examples of people roles ending in -er. Caterer, lecturer, carpenter etc.


The "or" suffix tends to be more common in American English. In English English, the "er" prefix is usually preferred when not referring to a person. In this instance I would certainly use Adapter.


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