4.6 Full point
The full point is also called full stop or, particularly in US use, period. Full points are used to mark the end of sentences, and in some classes of abbreviation. Do not use a full point in headings, addresses, or titles of works, even where these take the form of a full sentence:
All’s Well that Ends Well
Mourning Becomes Electra
If the full point of an abbreviation closes the sentence, there is no second point:
a generic term for all polished metal—brass, copper, steel, etc.
I came back at 3 a.m.