Continuing on my recent grammar and punctuation theme, I thought I'd create a short guide to comma rules.

The comma is unfortunately one of the most overused and misplaced punctuation marks. There are several grammatical situations that require the use of a comma, and that can make it a confusing for people and lead to its incorrect usage. Below are some of the most common situations that require the use of a comma.

To separate three or more items in a list

The shopping list included bread, milk, butter and cheese. A comma should not be included to separate the last two items of the list unless there is a danger of the two items merging and being indistinguishable without a comma. The deserts on the menu were apple crumble, strawberry tart, chocolate cake, and ice cream. In the sentence above a comma would be used after the word cake to indicate that the ice cream is a single item in the series. The use of the punctuation mark here is known as the ‘Oxford comma’, and is used to avoid causing any confusion for the reader.

Before some conjunctions

A comma should be used before the conjunctions ‘but’, ‘and’, ‘for’, ‘yet’, ‘nor’, ‘or’ and ‘so’ to separate independent clauses. He is a great footballer, but should learn to pass the ball more. A comma does not need to be used with the conjunction ‘because’, unless the sentence would be confusing without it.

To separate the introductory segment of a sentence

A comma should be used to separate the introductory element from the main body of a sentence. For example. As the sun began to set, the children stopped playing in the park and made their way home. The comma can be omitted if the introductory segment is very short, but should always be included if it modifies the meaning of the sentence or could cause confusion without it. Until the summer James will have to play inside after school. Until the summer, James will have to play inside after school.

To split the parenthetical elements of a sentence

The parenthetical element of a sentence is the part that is not essential to the overall meaning of the sentence. A comma is used to separate this part from the rest of the sentence. John, the best runner in the school, always finished first in the 100m sprinting race. It is important to ensure that the parenthetical element of the sentence is opened and closed with a comma.

To divide quotes or direct speech from the main body of a sentence

Commas are used to separate direct speech or quotes from the rest of a sentence. “Don’t jump on the sofa”, she shouted, “unless you want to spend the rest of the day in your room” A comma is not always needed if another punctuation mark separates the direct speech from the rest of the sentence. “Don’t jump on the sofa!” she shouted.

To separate contrasting elements of a sentence

A comma should be used to divide parts of a sentence that express distinction. The old car was beautiful, but not very well maintained.

To separate years and dates, cities and countries etc.

He lived in Brixton, South London. She was born on the 12th July, 1976.

To divide several adjectives in a sentence

A comma should be used to divide adjectives in a sentence if you could use ‘or’ or ‘and’ between them. The scruffy, dishevelled and clumsy man was actually the CEO of the company.