Use a period to end a complete sentence. A sentence is a group of words containing a subject and predicate. In British English a period is called a 'full stop'.Examples:
He went to Detroit last week.
They are going to visit.
There are a number of different uses for commas in English. Commas are used to:
o Separate a list of items. This is one of themost common uses of a comma. Notice that a comma is included before the conjunction 'and' which comes before the final element of a list.
I like reading, listening to music, taking longwalks, and visiting with my friends.
They would like books, magazines, DVDs, video cassettes, and other learning materials for their library.
o Separate phrases (clauses). This is especiallytrue after a beginning dependent clause or a long prepositional phrase.
In order to qualify for your certificate, you will need to take the TOEFL exam.
Although he wanted to come, hewasn't able to attend the course.
o Separate two independent clauses that are connected by a conjunction such as 'but'.
They wanted to purchase a new car, but their financialsituation would not allow it.
I'd really enjoy seeing a film this evening, and I'd like to go out for a drink.
o Introduce a direct quote (as opposed to indirect speech i.e. He said he wanted tocome ...).
The boy said, "My father is often away during the week on business trips."
His doctor replied, "If you don't stop smoking, you run the risk of a heart attack."
o Separateappositives (a noun, or noun phrase) or non-defining relative clauses.
Bill Gates, the richest man in the world, comes from Seattle.
My only sister, who is a fantastic tennis player, isin great shape.
The question mark is used at the end of a question.
Where do you live? How long have they been studying?