Rules for using periods include: 1. Use a period at the end of a complete statement sentence. 2. Do not use a period after an abbreviation that already ends in a period. 3. An indirect question ends with a period, not a question mark. Proper placement of periods includes putting the period inside the closing parenthesis if the parenthetical is a complete sentence, and outside if it is part of a larger sentence. The period goes inside the closing quotation mark even if the quotation does not end with a period. Some abbreviations use periods and some do not.

2. Periods
Rule 1. Use a period at the end of a complete sentence that is a
statement.
Example: I know him well.
Rule 2. If the last item in the sentence is an abbreviation that
ends in a period, do not follow it with another period.
Incorrect: This is Alice Smith, M.D..
Correct: This is Alice Smith, M.D.
Correct: Please shop, cook, etc. We will do the laundry.

3. Direct and indirect questions
• An indirect question ends with a period, not a
question mark.
Direct question: What is she doing tonight?
Indirect question: I wonder what she’s doing tonight.

4. Proper placement of the period
with parentheses
• If a sentence ends with a parenthetical that is only
part of a larger sentence, the period is placed
outside the closing parenthesis.
• Example Hotel rooms are likely to be in short
supply throughout August (the peak travel period).

5. Proper placement of the
period with parentheses
• If the parenthetical is itself an entire sentence, the
period is placed inside the closing parenthesis.
Example :
Their house was the largest one on the block. (It also
happened to be the ugliest.)

6. Proper placement of the period
with quotation marks
• If a sentence ends with quoted material, the period
is placed inside the closing quotation mark, even if
the period is not part of the original quotation.
The president’s speech both began and ended with
the word “freedom.”
Note, however, that if the quoted material itself
ends with a question mark or exclamation point,
the period is omitted.

7. Continue…
 Correct- Yesterday he asked, “Why is it so cold on
Mars?”
 Incorrect Yesterday he asked, “Why is it so cold on
Mars?”.

8. Abbreviations
• In addition to ending a sentence, the period is used
with certain abbreviations.
• The current style is to use periods with most
lowercase and mixed-case abbreviations
(examples: a.m., etc., vol., Inc., Jr., Mrs., Tex.)
and to omit periods with most uppercase
abbreviations (examples: FBI, IRS, ATM, NATO, NBC,
TX).

9. Abbreviations
• Note, however, that many scientific and technical
abbreviations are formed without periods,
• even when they are lowercase or mixed-case.
Examples: kHz (kilohertz), rpm (revolutions per
minute), kg (kilogram), Na (sodium), 1st (first).