The serial comma (also known as the Oxford comma or Harvard comma, and sometimes referred to as the series comma) is the comma used immediately before a coordinating conjunction (usually and or or, and sometimes nor) preceding the final item in a list of three or more items. For example, a list of three countries can be punctuated as either “Portugal, Spain, and France” (with the serial comma) or as “Portugal, Spain and France” (without the serial comma).
