Use a period to close sentences that make statements or give mild commands.

All books are either dreams or swords.

– Amy Lowell

Don’t use a fancy word if a simpler word will do.

– George Orwell, “Politics and the English Language”

Please close the door.

A period also closes indirect questions, which report rather than ask questions.

I asked how old the child was.

We all wonder who will win the election.

Until recently, periods have been used with most abbreviations in American English (see Chapter 46). However, more and more abbreviations are appearing without periods.

Some abbreviations rarely if ever appear with periods. These include the postal abbreviations of state names, such as FL and TN (though the traditional abbreviations, such as Fla. and Tenn., do call for periods), and most groups of initials (GE, CIA, AIDS, UNICEF). If you are not sure whether a particular abbreviation should include periods, check a dictionary, or follow the style guidelines (such as those of the Modern Language Association) you are using in a research paper.