just a quicky as I am writing a report. Is it “I gotta Ph.D…” or “I gotta Ph.D.” ? The first seems correct as one full stop is for the abbreviation and one for the end of sentence, but it still looks odd.
Correct. Do not use two periods unless you immediately proceed on to three. Four is right out.
whoops. sorry. That should be “INcorrect,” as in, use only one period at the end of the sentence: “I got a PhD.”
(if you’re going to worry about how many periods, worry about using “gotta”, too, unless PhD is an euphemism in your world for something you have to do…
In most cases, I go with the rule that you use a dot if letters are ommitted from the end of a word, but not if the abbreviation is a contraction with the last letter omitted. However, I would regard PhD as an exception, as it is pretty much a noun in its own right. I wouldn’t use any dots. I’d never use a double-dot, however!
Some abbreviations and acronyms do not take full stops/periods, such as NATO, IBM, and radar. Some require them. And in some cases they are optional.
When a full stop/period is present owing to an abbreviation at the end of a sentence, it’s sufficient to close a sentence in and of itself, and should not be doubled to “have one for the abbreviation and one for the sentence.”
On the other hand, in the case of ellipses, a row of three full stops/periods symbolizes the omission of words. When the omission is at the end of a sentence, one uses four rather than three, the first three representing the deleted text and the fourth the sentence closure.
Very rarely, in highly informal writing, six or more periods/full stops in a row will be used to represent the trailing off of a thought. Used highly sparingly, this can be an effective narrative device, but you can imagine …
I got a Ph.D.
would be the style I would use, although I see nothing wrong with the more modern “I got a PhD.”
And, as Ethilrist correctly pointed out “gotta” is normally used as a phonetic transcription of the phrase “got to” not “got a.”
I used gotta in an ironic sense
e.g. "I gotta Ph.D. in English " but it was obviously a bit too obscure
anyway got my report done thanks
gotta go
Don’t forget that the prevailing usage in British English tends to omit far more than in American English, particularly in the case of Mr and Mrs. Also, acronyms are often capitalized only on the first letter - Nato, Aids, and so forth.
I mention this because I wouldn’t be surprised if this eventually became prevailing usage in the United States as well; it’s a bit more modern and convenient.
I believe this has more to do with whether the acronym (as opposed to abbreviation) is considered a proper noun, and has very little to do with its status as an acronym. Note uncapitalized “radar.”
The principle I follow for acronyms is that of lissener - if it’s pronounced as a word, it isn’t all-caps. (Educational example - American SATs vs. English Sats). And words such as radar, laser and sonar have been absorbed into the vocabulary in their own right, as I suspect Aids will do at some point.
Just in case there are any of my fellow Yanks who don’t know what a full stop is, it’s what we call a period.
IIRC title abbreviations such as Mr. and Mrs. do not have to have the period according to British standards of style.
[Aside] This is why in some novels the characters say “stop” when reading or dictating a telegram. As in:
Bertie
hear you are coming here stop
when come bring book My Friends The Newts get any bookshop stop
Gussie
[/aside]
That was me, not lissener, who said that.
Oops - sorry! 
I seem to remember hearing that, according to the British standards of style, abbreviations take a period, but suspensions do not. Since ‘Mr’ is a suspension (i.e., letters are omitted not from the end but from the middle of the word), it doesn’t come with a period. Don’t know if that’s correct or not, though.