The comma is a humble punctuation mark, but its shape inspired the naming of one of the most colorful butterflies, the Comma.

This charming butterfly with a white marking on its underside that looks like a comma may help you to remember rules of English grammar. Why do we need commas at all? They separate sentences in ways that make them easier to understand for the reader. If you are writing an academic article or thesis, the whole point is to be understood by whoever reads you, so it is worth getting this detail correct to make sure what you produce is as understandable as possible. The TU Libraries own an entire book about the comma, but if you are short on time, the following brief hints may help:

Where commas do not belong.

In Thai English, all too often writers put commas in long sentences just because they somehow feel a comma should be there. This is not good reasoning. Also sometimes in Thai English, people put commas where they think a reader would pause to breathe if the sentence was read aloud. Again, this is not a useful guide for when to use commas.

Where commas are needed.

If you have a list of three or more things and a single conjuction (such as and), put a comma after each word in the list except for the last one.

My favorite cities are Rayong, Mae Sot, and Om Noi.

Members of my family live in Mae Hia, Mae Hong Son, Maha Sarakham, and Map Ta Phut.

He studied hard, took the test, and failed.

Parenthetic comments

Words that interrupt what you are saying but do not change the basic meaning of the sentence are called parenthetic expressions or comments. When these are added to a sentence, they should be put between commas.

Durian, for example, is not a good ice cream flavor.

Be sure that you put a comma before and after the parenthetic comment, to avoid mistakes such as:

Durian, for example is not a good ice cream flavor.

or

Durian for example, is not a good ice cream flavor.

Both of the above are wrong, since when you start a parenthetic comment, in this case the words for example, you must always show where it ends.

If you are writing phrases starting with the words where and when, commas are also useful:

In 1395, when Somdet Phra Ramesuan died, the people greeted the next king of the Ayutthaya Kingdom of Siam, Somdet Phra Rama Ratchathirat.

In the above sentence, the phrase or clause when Somdet Phra Ramesuan died is considered to be non-restrictive. That means it does not change the meaning of the rest of the sentence. Instead it adds information that might have been given to the reader in two separate sentences.

In 1395, Somdet Phra Ramesuan died. That year, the people greeted the next king of the Ayutthaya Kingdom of Siam, Somdet Phra Rama Ratchathirat.

This is useful to know when we consider that clauses which do change the meaning of the sentence never need commas.

The student who gets the best mark in the final exam will earn the highest grade in class.

In the above sentence, you cannot take out the words who gets the best mark in the final exam without changing the meaning. If you remove who gets the best mark in the final exam, you are left with a puzzling fragment, The student will earn the highest grade in class. Which student? It is not clear. So in this case, the information in the relative clause cannot be separated into two complete sentences, and so no comma is wanted or needed.

More places for commas.

If you write an independent clause with the words and or but before it, a comma should go before the and or but.

My mother threw out all my old homework exercises, and I cannot help my younger sister by giving her copies of the exams I took years ago.

I cannot help my younger sister with her studies, but she is smart enough to succeed on her own.

As with most examples of English writing, if you are in doubt, try to say the same thing in a different way that you are more comfortable with. It may be easier to remember when and where to use a comma if you phrase the above sentences this way:

Since my mother threw out all my old homework exercises, I cannot help my younger sister by giving her copies of the exams I took years ago.

Even though I cannot help my younger sister with her studies, she is smart enough to succeed on her own.

If you have written two independent clauses, do not put a comma between them. If there are two separate statements, make them into two distinct sentences. Sometimes in Thai English we see mistakes such as

Krabi province is home to some of Thailand’s most famous beach destinations, Railay is the best of them.

The above is wrong, but can be stated correctly either as

Krabi province is home to some of Thailand’s most famous beach destinations, and Railay is the best of them.

or

Krabi province is home to some of Thailand’s most famous beach destinations. Railay is the best of them.

If you have the slightest concern that your sentence may be wrong, just state it a different way.

Use commas to avoid breaking up continuous thoughts into choppy sentence fragments.

The following is in bad English:

Ayutthaya is located only a short bus trip or train ride from Bangkok. Making it convenient for a day trip if you’re pressed for time.

The above should be one sentence, with the different parts separated by a comma:

Ayutthaya is located only a short bus trip or train ride from Bangkok, making it convenient for a day trip if you’re pressed for time.

Quoting someone.

If your article or thesis in English mentions the exact words stated by someone, a comma must be placed before the first quotation mark. The last quotation mark goes after the full stop at the end of whatever you are quoting:

In Thale Haeng Nueng, Chit Burathat wrote, “The evening settles as the sun crosses the sky.”

In MLA format bibliographies.

If you must reverse the order of an author’s name, then it must be cited as last name, comma, first name:

If the book or article you are citing has two or more authors, reverse the order of the name of the first author you mention and write the other authors’ names in the usual way:

Martin, M. Marlene, David Levinson, and Ian Skoggard. “Cultural Summary: Central Thai.” eHRAF Collection of Ethnography. Web. 26 Feb. 2010.

(all images courtesy of Wikimedia Commons).