Use a period to end all sentences except direct questions or genuine exclamations. Also use periods in abbreviations according to convention.
Reported or indirect question
If a sentence reports a question instead of asking it directly, the sentence should end with a period, not a question mark.
Mild exclamation
If a sentence is not a genuine exclamation, it should end with a period, not an exclamation point.
Common uses of periods in abbreviations
Mr. |
i.e. |
a.m. (or AM) |
Ms. |
e.g. |
p.m. (or PM) |
Dr. |
etc. |
Common omission of periods in abbreviations
NO PERIOD IN US POSTAL SERVICE ABBREVIATIONS FOR STATES
MD |
TX |
CA |
NO PERIOD IN ABBREVIATIONS FOR ORGANIZATION NAMES
NATO |
UNESCO |
UCLA |
BS |
BC |
IRS |
AFL-CIO |
NIH |
PhD |
AD |
USA |
NAACP |
SEC |
RN |
BCE |
NO PERIOD IN ABBREVIATIONS OF ACADEMIC DEGREES
BS |
PhD |
RN |
NO PERIOD IN ABBREVIATIONS FOR ERAS
BC |
AD |
BCE |
NO DOUBLE PERIODS
If a sentence ends with a period marking an abbreviation, do not add a second period.
NOTE:Check the style of the discipline in which you are writing for the preferred use of periods with abbreviations.
Exercise:
End punctuation
Related topics:
Abbreviations
Style guides for various disciplines