Periods end declarative sentences and requests or mild commands.

Declarative: His name is Joshua.
Request or Mild Command: Please be sure to tell her I am coming.

Periods are used to end most abbreviations except for acronyms and abbreviations which are pronounced. See Abbreviations Contents for more information.

If a sentence ends with an abbreviation, no additional period is needed. If the sentence requires a question mark or exclamation point, one may be added after the period.

Incorrect: Please make the check out to Roland N. Payne, D.D.S..
(Second period at end not needed)
Correct: Please make the check out to Roland N. Payne, D.D.S.

Correct: Do I make the check out to Roland N. Payne, D.D.S.?

A period is used after numbers and letters in outlines.

Outline:
I. Punctuation
A. Periods
1. End sentences
2. Abbreviations

3. Outlines

A period always comes before a closing quotation mark.

Incorrect: George said, “I don’t get it”.
Correct: George said, “I don’t get it.”