The area code for a particular city or region is the series of numbers that you have to dial before someone's personal number if you are making a telephone call to that place from a different area.
[mainly US]
The area code for western Pennsylvania is 412.
regional note: in BRIT, use dialling code
area code in British English
noun
a number prefixed to an individual telephone number: used in making long-distance calls
area code in American English
US
any of the three-digit telephone codes assigned to each of the areas into which the U.S., Canada, etc. are divided
Examples of 'area code' in a sentence
area code
You can sometimes opt to have a number with an area code different from where you are based.
Times, Sunday Times (2007)
More than two million landline users will have to dial area codes for local calls after the supply of new numbers ran out.
Times, Sunday Times (2013)
The regulator has issued 400 million numbers across 610 area codes over the past century and the number of landlines used is in steep decline.