Okay, when I see acronyms I usually see stuff like NYOB, OMG, PM, stuff like that. I also see some of them with periods on them like N.A.S.A. Do you put the dots in them, or not?

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    From Wikipedia: en.wikipedia.org/wiki/Acronym#Punctuation You only put .s if it is an acronym in which you pronounce each letter, as in K.G.B. (Kay-Gee-Bee). – Riley Francisco Nov 26 '15 at 5:15
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    @Rathony +1. The .'s don't apply here. It is just NASA, isn't it? – onlyforthis Nov 26 '15 at 5:26
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    I linked to Wikipedia, I never said NASA uses .'s. – Riley Francisco Nov 26 '15 at 5:52
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    The science book you are reading might be for intermediary-level English speakers. There is no harm in using it. – user24743 Nov 26 '15 at 5:52
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    @RileyF - If you pronounce each letter, then I wouldn't classify that as an acronym, but as an abbreviation (or, to be more specific, as an initialism). – J.R. Nov 26 '15 at 8:49

This is something that has varied with time. I believe that it was once more common to include dots in initialisms (such as F.B.I.) or acronyms (such as U.N.I.C.E.F.), but I think you'll have a harder time finding contemporary news articles with acronyms or initialisms using dots like that nowadays – at least, it was easier for me to find articles with letters in all caps (e.g., FBI, UNICEF).

For example, on a UNICEF website, a Wikipedia page, and in article found in The Atlantic, all usages of the acronym are spelled as UNICEF (no dots), and many other abbreviations can be found in a similar form on those same pages, such as CEO, IGO, IFRC, UN, and NASCAR. That said, the Wikipedia page is a little inconsistent in this regard with respect to the abbreviation FC (football club): Sydney FC is listed with no dots, while Olympiacos F.C. (from Greece) and Rangers F.C. (from Scotland) are listed with the periods included.

The Grammar Girl blogger says this (emphasis added):

There's no strict rule about putting periods after each letter in an acronym or initialism. Some publications put periods after each letter, arguing that because each letter is essentially an abbreviation for a word, periods are necessary. Other publications don't put periods after each letter, arguing that the copy looks cleaner without them, and that because they are made up of all capital letters, the fact that they are abbreviations is implied.

In the past couple decades, contemporary typesetters seem to be favoring "cleaner" conventions. One common exception seems to be U.S., but that may be in part because of its similarity with the word us; consider these two sentences:

U.S. lawmakers debated the matter late into the night.
Us lawmakers debated the matter late into the night.
US lawmakers debated the matter late into the night.

The first two are easy enough to figure out, but some might argue that the third one could be confused with the second.

A different blog post from the Grammar Girl says this:

In American English, we always put a period after an abbreviation; it doesn’t matter whether the abbreviation is the first two letters of the word (as in Dr. for Drive) or the first and last letter (as in Dr. for Doctor).

British writers, however, make a distinction: abbreviations that are written with the first and last letter of the word (as in Dr for Doctor and Mr for Mister) do not get a period.

Heavens to St Peter! This just goes to show how muddled conventions like these can be.

  • "British writers, however, make a distinction: abbreviations that are written with the first and last letter of the word (as in Dr for Doctor and Mr for Mister) do not get a period." That's simply not true. We still write "Dr. Firstname Lastname". – Lightness Races in Orbit Oct 27 '18 at 22:13

There is no strict rule on using periods (full stops) in acronyms. You don't see N.A.S.A, B.B.C, or N.A.T.O often because they are so popular/familiar. However, you might have to put the periods if an acronym you use is not that familiar with readers.

You usually write Government Issue as G.I. because GI could be misunderstood as a typo or other words. G.I. means a US soldier. It is also common to write the United States as U.S.A.

It depends on your style, preference and how you define familiarity because what is familiar with one group of people might not be that familiar with other groups.

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    You also don't see "N.A.S.A." because it's pronounced as an acronym, not an initialism. – Fabien Snauwaert Nov 8 '18 at 15:32

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