Commas set off the elements of an address except for zip codes.

• Write to Bureau of the Census, Washington, DC 20233.
  
• In Needles, California, their luck ran out.
  

When a city name and state (province, country, etc.) name are used together to modify a noun that follows, the second comma may be omitted but is more often retained.

• We visited their Enid, Oklahoma plant.

but more commonly

• We visited their Enid, Oklahoma, plant.
  

Commas set off the year in a full date.

• On July 26, 1992, the court issued its opinion.
  
• Construction for the project began on April 30, 1995.
  

When only the month and year are given, the first comma is usually omitted.

• In December 1903, the Wright brothers finally succeeded in keeping an airplane aloft for a few seconds.
  
• October 1929 brought an end to all that.
  

A comma groups numerals into units of three to separate thousands, millions, and so on.

• 2,000 case histories
  
• 15,000 units
  
• a population of 3,450,000
  
• a fee of $12,500
  

Certain types of numbers do not contain commas, including decimal fractions, street addresses, and page numbers.

• 2.5544
  
• 12537 Wilshire Blvd.
  
• page 1415

A comma separates a surname from a following professional, academic, honorary, or religious degree or title, or an abbreviation for a branch of the armed forces.

• Amelia P. Artandi, M.D.
  
• Robert Hynes Menard, Ph.D., L.H.D.
  
• John L. Farber, Esq.
  
• Sister Mary Catherine, S.C.
  
• Admiral Herman Washington, USN
  

A comma is often used between a surname and the abbreviations Jr. and Sr.

• Douglas Fairbanks, Sr. or Douglas Fairbanks Sr.
  
• Dr. Martin Luther King, Jr. or Dr. Martin Luther King Jr.

A comma is often used to set off corporate identifiers such as Incorporated, Inc., Ltd., P.C., and L.P. However, many company names omit this comma.

• StarStage Productions, Incorporated
  
• Hart International Inc.
  
• Walsh, Brandon & Kaiser, P.C.
  
• The sales manager from Doyle Southern, Inc., spoke at Tuesday's meeting.