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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?

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So as "adapt" comes from latin (albeit second hand via French) then the "or" suffix should be more correct. – James Anderson Apr 25 '11 at 10:08
“In my current project we are writing a program to convert a newer protocol to an older one... the team cannot agree which spelling to use: adapter or adaptor.” — it’s always issues like this that are hardest to settle on, isn’t it? – Paul D. Waite Apr 25 '11 at 10:15
According to this link en.wiktionary.org/wiki/-or#Suffix the "or" suffix does strictly refer to a person so my original instinct to go for the "er" suffix for a program/device was probably correct! – James Anderson Apr 25 '11 at 10:32
@James Anderson: There's probably a strong tendency to use "-or" just for people, but it's not a hard-and-fast rule - otherwise object-oriented programming languages would have "constructers" and "destructers" instead of constructors and destructors :) – psmears Apr 25 '11 at 10:56
up vote 5 down vote accepted

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 :).

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Thanks for all the help. I think Billares links sent me off in the right direction! – James Anderson Apr 25 '11 at 10:35
Really? I have never, ever seen "adapter". – Marcin Apr 25 '11 at 13:21
@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 '11 at 14:23
Clearly, it is not uncommon, but it's still a new one on me. – Marcin Apr 25 '11 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). – Richard Haven Dec 17 '12 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.

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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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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.

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I tend to agree with all the talented linguists that the suffixes are used interchangeably; however, from my modest experience, the -or is used more frequently for people while the -er, for things/items. I do not have enough official evidence either to prove or disprove the fact that one is used more in the US and the other in the UK, but it is all possible... since we have other influences on the living language; technology, environment, globalization, robotics, etc. are all creating new versions and meanings we may not have heard before and thus, need to be open to those usages as the language - I would even attempt to say, the new language - is being expended and created not only in the textbooks but in various genre of literature. Thank you.
Dr. M.

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An interesting observation, but not an answer – Michael Owen Sartin Jan 15 '14 at 9:10

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