period--句号

Period (Full Stop)
1. The period is used at the end of a declarative sentence.
U.S. President Barack Obama has been awarded the 2009 Nobel Peace Prize.
Period
2. Use a period at the end of a mildly imperative sentence.
In case of tremors, leave the building immediately.
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Period
3. Use a period at the end of an indirect question.
English Writing
Punctuation
Comma
a series of words or phrases adverbial clause/phrase a compund sentence connected by and, but, or, for, so, nor, yet parenthetical elements (including appositives) nonrestrictive clauses transition words (such as therefore, however, moreover, furthermore, and consequently) geographical names date Sir, Madam
His father used to wonder why Barry’s head was so big. She asked if she could join us.
Period
4. The period is used with some abbreviations.
Mr. Mrs. Ms. a.m. p.m. FBI CIA IOU NBC
--- Do you enjoy living in Washington D.C.? --- Yes, very much.
Period
Notice that full stops should not be used in titles, headings, or subheadings.
I Know I Know You
Period
Notice that no full stop is required if a sentence ends with a title which contains its own punctuation such as a question mark.
I have already read Jeff’s Have You Been to Jamaica? He is the editor of Which?
Period
On the other hand, when an abbreviation ends a question or exclamation, it is appropriate to add a question mark or exclamation mark after the abbreviationending period.
Period
Notice that when the period ending the abbreviation comes at the end of a declarative sentence, it is also used to end the sentence.
John grabbed a cup of coffee and left for office at 7 a.m.