PERIOD:
The use of periods as punctuation in writing.
The primary uses of the period are:
a) At the end of a sentence, when the sentence is a statement or instruction.
Example:
Please have those reports completed and on my desk by Friday.
b) After an abbreviation or after initials.
Examples:
Gov’t. etc. I.R.S. John W. Smith
c) It is acceptable to omit the period after an abbreviation that consists of the first and last letter of a word.
Examples:
Mr. or Mr
Dr. or Dr
d) When abbreviating, for example calendar months, titles, degrees, or days of the week, it should be remembered that only one space follows the period at the end of the abbreviation, and that no spaces follow the letters within the abbreviation.
Examples:
U.S.A. not U.S.A
Ph.D. not Ph.D.
e) If a sentence concludes with an abbreviation that ends with a period, a second period should NOT be used
Example:
This matter will now be referred to the I.R.S.