Sentences ending with something that already contains a period/full-stop [duplicate]

Question

What's the rule about sentences that end in something that already has a period in it?

Like a sentence that ends in: Washington D.C. -or- etc.

Personally, and I realise this is wrong, I would love to have two periods - the first being, of course, the mark for the abbreviation and the second being the period/full-stop of the sentence.

I'm guessing that it is just treated as a stone that kills two birds, but I've never heard a definite answer as to how to deal with these.

Answer 1

Yes, punctuation can feel illogical. In fact, there are different standards across English-speaking countries, such as the U.S. and Australia. But wherever you are, it's one period only. Period.