Punctuation marks are used to help comprehension. They separate groups of words for emphasis and clarify the meanings of sentences. They take the place of the pauses and variations in tone, emphasis, and volume that we use when we speak. The comma is the punctuation mark that causes us the most difficulty. Perhaps, this will help.
Here are some of its principal uses:
- To separate principal clauses joined by a conjunction.
- The regular season lasted about eight months, but the playoffs took an additional one to two months.
- To separate portions of long compound predicates.
- The marketing executive prepares a detailed annual plan, budget, and forecast during the fall and, when the document has been approved, proceeds to implement all activities specified in the plan within the dates promised and the funds approved.
- To separate subordinate clauses and phrases that begin a sentence
- Having left home at an early age, he acquired extensive experience in his chosen field long before he had reached thirty years of age.
- There is no need to set off the clause or phrase by commas if it modifies a noun. That is, if its deletion would change the meaning of the noun.
- To set off modifying phrases that follow the word or phrase they modify.
- William, still lost in his book, was unaware that his dog had slipped away to investigate a low thump in the kitchen.
- To set off a participial phrase that has a subject and is independent of the remainder of the sentence.
- Having finished his last sales call for the day, David turned his car around and headed towards the city.
- To set off introductory, parenthetical, or interrupting elements.
- Naturally, we would be happy to accommodate you.
- The return trip, in contrast, may involve some hardship.
- To set off words or phrases that introduce examples.
- He is thinking of tropical country, such as Jamaica.
- She is interested in the winter sports, namely, skiing and skating.
- To set off words in a direct address.
- Should you choose to accept this assignment, Mr. Jones, you will be on your own.
- To set off contrasting expressions within a sentence.
- You are entitled to three weeks of vacation, not four.
- To separate words, phrases, or clauses in a series.
- Cars, trucks, and buses waited on the wharf for the afternoon ferry.
- To separate two or more adjectives, two or more, adverbs, or two or more phrases, which modify the same word or phrase.
- Work began in a relaxed, unhurried fashion.
- To set off a direct quotation. (If an exclamation mark or question mark follows the quotation, it replaces the comma.)
- "Don't expect to see me tomorrow," Charles growled as he turned on his heel to leave.