SOME ABBREVIATIONS require a full stop after them, and some don’t. How can you tell? Why is ‘Mister’ abbreviated to ‘Mr’, when abbreviating ‘Professor’ to ‘Prof.’ requires one?
There’s a simple rule. If the abbreviation ends in the same letter as the word it’s contracting, then no full stop is needed. So Dr Kildare doesn’t need one, while both Cmdr Bond and Sgt Bilko would report to Gen. Custer.
