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Question pretty self-explanatory. Should the abbreviation of the Latin term philosophiae doctor be written as PhD (no periods) or Ph.D. (with periods)?

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You have a couple of correct answers below. Personally I avoid periods in abbreviations, so I would use PhD, just as I would say Washington DC using the postal code abbreviation DC rather than the historical abbreviation D.C. (District of Columbia). – Wayne May 17 '11 at 12:38

5 Answers 5

up vote 20 down vote accepted

Actually both are correct, I could easily found both on my NOAD, and there's plenty of pages on the net where you find it written as "PhD".

The OALD gives an interesting distinction, stating that Ph.D. is especially North American English.

Now, being a non-native speaker, I can only rely on official sources to state who uses what, but there's no doubt that both variants are used.

Lastly, I think there's really no point in distinguishing them as "Philosophiae Doctor" or "Doctor of Philosophy" because it's the same exact expression, although considering the abbreviation, the former is the correct and original long version, the latter is just the English translation.

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Collins English Dictionary shows a separate abbreviation if you want to specify the degree in English: "DPhil". (Also at, just further down the page.) – MT_Head May 17 '11 at 9:52
@MT_Head: Thanks for commenting. With "if you want to specify the degree in English" you mean "being unambiguous"? – Alenanno May 17 '11 at 9:54
Indeed. To give an anecdotal example: in the company I used to work for, which was British, people didn't tend to use periods for abbreviations of degrees, e.g. MSc, PhD. I now work for an American company, where the convention is to use them, hence Ph.D. – Steve Melnikoff May 17 '11 at 9:55
I see, I was thinking of that before honestly, since PhD (or PHD) can be other things too... Thanks for pointing it out! – Alenanno May 17 '11 at 10:04
@MT_Head DPhil is also what a PhD is called at Oxford. If you use DPhil then a BE speaker would assume you specifically mean Oxford. – mgb May 17 '11 at 15:07

PhD and Ph.D. are both correct. Canadians tend to omit the periods and those from the U.S. tend to keep them.

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Might you have any source citations or additional references for that? I think your answer is correct, but a little more detail, doesn't actually need to be a link, would be helpful. – Ellie Kesselman Nov 18 '11 at 18:29

I tend to use both 'PhD' and 'Ph.D'. A DPhil is awarded at both Oxford Uni and Sussex Uni in England. All others award PhDs to my knowledge.

It bugs me when people use 'Dr' before their name and then also state the award following it. I feel it should be one or the other.

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I remember discussing this with a trained secretary a long time ago. We eventually decided that the use of camel case (starting each abbreviated word in upper case) removes the need for the periods when abbreviating titles. However, when an abbreviation is relatively new or used in an unusual context, the periods help to avoid ambiguity.

For my own use, the overriding consideration is 'house style'. It is more important for a document to be internally consistent, to avoid confusion.

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Bobble's "house style" consideration typically applies not just to a single document but also, as the name implies, to all documents emanating from the same "house". For example, my academic discipline (linguistics) traditionally employs the no-periods convention for all titles (not only PhD, MA, and BA but also Mr, Dr, and Prof), while the style enforcer at my academic institution (an American university) insists that I sprinkle periods around (for a total of 9 in my 6 examples). – H Stephen Straight Feb 12 '13 at 22:32

The most common I have seen are:

  • Ph.D
  • PhD

I have rarely come across a Ph.D. (with two periods).

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Ugh. Ph.D looks like the inconsistent worst of all worlds. – user1579 May 17 '11 at 16:57

protected by RegDwigнt Jul 1 '12 at 12:28


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