Punctuation: Period
A period ( . ) is a form of punctuation used to end a declarative sentence. Periods are frequently, but not always used, after initials and with two-letter abbreviations (U.S.).
Declarative sentence: Harry S Truman did not use a period after his middle initial.
Periods should be placed inside closing quotation marks, except when followed by a parenthetical note.
Example: Abraham Lincoln said, "Those who deny freedom to others, deserve it not for themselves; and, under a just God, can not long retain it."
When used in email and Web addresses, periods are pronounced "dot" (wmich dot edu).