The period

Use a period to end all sentences except direct questions or genuine exclamations. Also use periods in abbreviations according to convention.

to end sentences Most sentences should end with a period. A sentence that reports a question instead of asking it directly (an indirect question) should end with a period, not a question mark.

If a sentence is not a genuine exclamation, it should end with a period, not an exclamation point.

in abbreviations A period is conventionally used in abbreviations of titles and Latin words or phrases, including the time designations for morning and afternoon.

note: If a sentence ends with a period marking an abbreviation, do not add a second period.

Do not use a period with postal abbreviations for states: MD, TX, CA.

Current usage is to omit the period in abbreviations of organization names, academic degrees, and designations for eras.

The question mark

A direct question should be followed by a question mark.

tip: Do not use a question mark after an indirect question, one that is reported rather than asked directly. Use a period instead.

The exclamation point

Use an exclamation point after a word group or sentence to express exceptional feeling or to provide special emphasis. The exclamation point is rarely appropriate in academic writing.

tip: Do not overuse the exclamation point.

This sentence doesn’t need to be pumped up with an exclamation point. It is emphatic enough without it.