What is a serial comma and how do I use it?
Serial commas punctuate a series of elements (words, phrases or clauses). Problems with serial commas sometimes arise when it comes time to punctuate the final elements in a list. For example:
While a comma before the final and is optional, a comma can alter the meaning. The first example can be read as meaning "Samira is lovely because she is tall and lean," or it can be interpreted to mean "Samira is lovely and tall and lean." The second example with a comma before and makes the meaning clear.
When meaning is clear, the comma before the final and or or may be omitted, as in the following examples:
If there are a number of items in a list and omitting the final comma could result in confusion or a lack of clarity, opt for a comma. For example:
The final comma indicates that a cheese and bacon sandwich is what Eileen likes to eat. If we remove the last comma, the reader may infer that one of Eileen's favourite foods is a ham and cheese and bacon sandwich.