The single period does double duty-marking the abbreviation and closing the sentence.

Punctuating an Abbreviation at the End of a Sentence: Use a single period when an abbreviation appears at the end of a sentence.

Placing a Period After Each Letter in an Acronym or an Initialism: Though there are exceptions, as a general rule omit the periods: NATO, DVD, IBM.

at the end of a list introduced by 'such as' or 'including.' (short for et cetera) means 'and others.' Never write 'and etc.' Do not use etc.

Using the Abbreviation Etc.: The Latin abbreviation etc.

As a general rule, don't abbreviate the month if it appears alone or with just the year-and don't abbreviate the days of the week unless they appear in charts, tables, or slides. 14), abbreviate months as follows: Jan., Feb., Mar., Apr., Aug., Sep.

Abbreviating Months and Days: If the month is preceded or followed by a numeral (14 Aug.

comes before it, but nowadays the abbreviation commonly follows the year in both instances. Use capital letters or small caps for B.C. Unless your style guide says otherwise, use lower case or small capitals for a.m.

Using Common Abbreviations: Certain abbreviations are never spelled out: a.m., p.m., B.C.Jan Jones, M.D.) For nonmedical doctors, write Dr. Abbreviating the Titles of Doctors: For medical doctors, write either Dr.Placing a Period at the End of an Abbreviation: In American usage, an abbreviation that includes the first and last letters of a single word (Doctor, for example) is usually followed by a period (Dr.), while In British usage, the period (or full stop) is usually omitted (Dr).Use 'an' before a vowel sound ('an ABC documentary' or 'an MRI'). Use 'a' before a consonant sound (for example, 'a CBC documentary' or 'a U.S. Using Indefinite Articles Before Abbreviations, Acronyms, and Initialisms: The choice between 'a' and 'an' is determined by the sound of the first letter in the abbreviation.

10 Tips for Using Abbreviations Correctly

How to find the abbreviations for words