Punctuation is a device in writing to help your readers understand better what you have expressed in your writing. There are certain punctuation rules you need to follow in order to make your meaning clear and your sentences effective.
(1) The comma is used for clarity in separating different parts (words, phrases, or clauses) of a sentence.
e.g. The box contained some nails, a pair of cloves, and a hammer.
The comma before and is optional, but is preferable where clarity may be an issue. The comma is not omitted before and in a series of independent clauses.
e.g. The father took the key, his children carried the bag, and their dog followed them.
(2) The comma separates independent clauses joined by a coordinating conjunction (but).
e.g. This is an excellent movie, but many people have not seen it.
(3) The comma separates a dependent clause from an independent one.
e.g. Although this is an excellent movie, many people have not seen it.
(4) The comma separates coordinate adjectives (describing the same noun) without the conjunction and.
e.g. a tall, dark, handsome man (coordinating adjectives)
However, the comma is omitted in cluster adjectives (describing the subsequent words)
e.g. a dark brown leather jacket (dark describes brown; brown describes leather; and leather describes jacket)
(5) The comma is used for clarity of meaning.
e.g. At sixty-five, you may consider retirement.
e.g. Not getting any sleep, the man felt exhausted.
e.g. To write effectively, you must learn some basic writing skills.
(6) The comma separates a non-essential clause or sentence element from the rest of the sentence.
e.g. Look at this book, which was found on the kitchen floor!
There is only one book here, and it was found on the kitchen floor; which was found on the kitchen floor becomes only additional but not essential information (indicated by the presence of the commas).
Look at another example:
e.g. Look at this book that was found on the kitchen floor!
There are many other books, and this one was found on the kitchen floor; that was found on the kitchen floor is essential information because it identifies which book to look at (indicated by the absence of the commas).
(7) The comma separates modifiers and conjunctive adverbs.
e.g. He was helpful. For example, he always helped in the kitchen.
e.g. He was a fast runner. In fact, he was the fastest on record.
e.g. There are several things you must do. In the first place, you must have the mindset to be diligent.
e.g. He wanted to pass the exam. Therefore, he worked extra hard.
e.g. She was beautiful. Moreover, she had a taste for fashion.
e.g. He is always helpful. Nevertheless, this time he did not lift a finger to help me.
e.g. He knew he was wrong. Thus, he apologized right away.
(8) The comma is NOT used before subordinating conjunctions (after, although, because, before, if, since, unless, until, when, where).
e.g. You cannot leave now because the airport is closed. (NO comma)
e.g. Because the airport is closed, you cannot leave now. (comma here)
e.g. Do not call 911 unless it is an emergency. (NO comma)
e.g. Unless it is an emergency, do not call 911. (comma here)
e.g. We left the bar when we finished our drinks. (NO comma)
e.g. When we finished our drinks, we left the bar. (comma here)
Copyright© by Stephen Lau