The Dos and Donts of Using a Period

Pay attention!

1. If you write a complete sentence enclosed in parenthesis standing alone (as an extra comment or after thought you want to add after the end of the first sentence), start it with a capital letter and end it with a period.
When the new recruit heard that he was accepted to the marines, he was very disappointed. (He had originally hoped to serve in the navy.)

2. However, If you write a complete sentence enclosed in parenthesis (as an inside comment) which is embedded in the surrounding sentence, you should not start it with a capital letter and not end it with a period.
When the new recruit heard that he was recruited to the marines (he had originally hoped to serve in the navy), he was very disappointed.

Note: You cannot put two or more complete sentences in parenthesis. For separating different phrases within parenthesis, use a colon, semicolon, dash or conjunction but never a period.

New army recruits consider several service options (among which are joining the navy, volunteering to become medics or doing office jobs) before actually being assigned to their position.


3. Do not use a period to end a sentence in a dialog when more text follows (e.g. a phrase telling who is being quoted). Use a comma instead and put it in the quotation marks.
"You will be recruited to the Marines," said the recruitment officer.

4. Do not end a sentence with a period if it already ends with another end punctuation mark (a question mark or an exclamation point).
Soldiers must obey their commanders' orders! (No extra period)

5. Do not use a period to end a sentence which ends with an abbreviation which itself ends with a period. Typical abbreviations which end with a period are: Mr., Mrs., Ms., St. (street or Saint), Mt. (mountain), Dr., Jr., Fri., Feb., a.m. and p.m. (Note: Do not abbreviate professor to Prof. in academic writing).
After a career in the army, she went on to work for Time Warner Inc. (no extra period)

6. However, you can use a question mark or an exclamation point to end a sentence ending with an abbreviation which itself ends with a period.
Do the soldiers have to sign in at 7:00 a.m.?

7. When listing items in a vertical list, consider ending each item on the list with a period, or not. We at WhiteSmoke advise to use periods if the items are complete and/or long sentences, and no periods if the items are just short phrases. Whatever you choose, remember to be consistent. If the items are numbered, use periods to separate the numbers from the text.

  • Ingredients for a salad:
  • 1. Cherry tomatoes.
  • 2. Mini cucumbers.
  • 3. Olive oil and vinegar.


Or,

  • Ingredients for a salad:
  • 1. Tomatoes
  • 2. Mini cucumbers
  • 3. Olive oil and vinegar


Pay attention!
Use a period for abbreviations which do not fall into any of the above mentioned categories.
For example:

  • anonymous anon.
  • continued cont.
  • editor Ed.

Other Uses of the Period


1. Use the period to set off list numbers in numbered vertical lists. You can also use closing parenthesis.

  • Ingredients for a salad:
  • 1. Cherry tomatoes.
  • 2. Mini cucumbers.
  • 3. Olive oil and vinegar.


or

  • Ingredients for a salad
  • 1) Cherry tomatoes
  • 2) Mini cucumbers
  • 3) Olive oil and vinegar


2. Use the period to set off headings, subheadings and in figure or table captions and identifiers.

  • The period. The period has the following uses
  • Table 8. Summary of the Uses of the Period


3. Use a period for the decimal point in English (a comma is used in other parts of the world).
There is a 46.6 % increase in sales and 5.8% decline in customer complaints.

3. Always use periods in people's names.
C.S. Lewis (the author of 'The Chronicles of Narnia')
Franklin D. Roosevelt (former U.S.A. president)

4. Use periods with titles and honorifics.

  • Mr. Magoo
  • Mrs. Smith (for a married woman)
  • Dr. Seuss
  • Main St. (street)
  • Mount St. Helen (saint)
  • William Park, Esq.
  • WhiteSmoke, Inc. (incorporated)
  • Sam Davis, Sr. (senior - the father)
  • Sam Davis, Jr. (junior- the son)


Note: Use Miss (an old-fashioned title for an unmarried woman or for referring to young women or waitresses) without a period. Miss. with a period stands for Mississippi.
Miss America comes from Miss.

Use Ms. (a modern title for women used regardless of their marital status) with or without a period.
Ms. Smith or Ms Smith

Note: The period is optional for academic degrees. Whatever you choose, remember to be consistent.
M.D. or MD (Doctor of Medicine)
B.A. or BA (Bachelor of Arts)

5. The use of the period in geographical names is optional. Whatever you choose, remember to be consistent.

  • U.S.A. or USA
  • U.K. or UK
  • N.Y.C or NYC


Note: For American states and Canadian provinces use periods only for the shortened form and not for the two-letter postal abbreviation. For two-word names, only one abbreviated form applies, in which the period is optional.

  • CT Conn. Connecticut
  • WA Wash. Washington
  • N.S. NS Nova Scotia


6. Use of periods in time indicators is optional. Whatever you choose, remember to be consistent.

  • A.M. or AM
  • B.C. or BC
  • A.D. or AD


Note: written in lower case, a.m. is used with periods, not to be confused with "am"

7. Do not use periods in metric measurements

  • 200 km
  • 180 cm
  • 48m2


8. Do not usually use periods in abbreviations for company and organization names, unless convention requires it.

  • NATO
  • IBM
  • CBS


9. Pay attention to the use of the period in Latin abbreviations.

  • e.g. - exempli gratia (meaning for example)
  • i.e. - id est (meaning that is)
  • et al. - et alia. (meaning and others)
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