1. The English House of Commas
This set of slides will illustrate the most common uses of one of the most common punctuation marks:
THE COMMA

2. The English House of Commas
Use a comma to set off the elements of a series (three or more things), including the last two.
My favorite uses of the Internet are sending , surfing the Web, and using chat rooms.
You may have learned that this comma is not necessary.
Sometimes, however, the last two items in your series will flow into one if you don’t use the “serial comma”.

3. The English House of Commas
Use a comma and a coordinating conjunction (“fanboys” = for, and, nor, but, or, yet, so) to connect two independent clauses.
A lot of students speak English pretty well, but writing is a skill that many have problems with because they don’t practice.
If the two independent clauses are brief and nicely balanced, this comma may be omitted, but the comma is always correct.
Your speaking is OK but your writing isn’t.

4. The English House of Commas
Use a comma to set off introductory elements.
Because he doesn’t write English well, he wasn’t able to get the internship he had hoped for.
Although she said she had written the essay herself, the teacher found the same text on the Internet and saw she had plagiarized it.
If the introductory element is brief and the sentence can be read easily without the comma, it can be omitted.
On Monday we’ll review for the exam.

5. The English House of Commas
Use a comma to separate coordinate adjectives.
Teachers grew weary of working in the drafty, dreary, dilapidated computer room.
The plans for an expensive, modern computer center should make them happy.
If you could put a but or an and between the adjectives, you should put a comma between them.
expensive and modern = expensive, modern But not “a slow and old laptop.” “A slow old laptop” would be correct.

6. The English House of Commas
Use a comma to set off elements that express a contrast or a turn in the sentence.
The essay was interesting, but too long for the assignment.
The teacher wanted something original, not from the Internet.

7. The English House of Commas
Use a comma to set off states and countries, years (in a full date), titles, etc.
The conference was originally set for Geneva, Switzerland, but was then rescheduled for Chicago, Illinois.
The seminar was scheduled for August 5, 2011, in the college auditorium in Newton, Massachusetts.
Joe Greenman, an English teacher in Berlin, has three cats.

8. The English House of Commas
Use a comma to set off quoted language.
The helpful teacher explained, “Please remember to use your spelling checker before you send me your homework.”
“I always use it”, said the best student.
“I tried to install one”, said a student, “but I use Linux, and I couldn’t find one that works on my computer.”

9. The English House of Commas
Use a comma to set off parenthetical elements. This is the most difficult rule in comma usage.
A parenthetical element is “added information,” something that can be removed from a sentence without changing the essential meaning of that sentence.
Deciding what is “added information” and what is essential is sometimes difficult. See the next slide.

10. The English House of Commas
Parenthetical elements:
When an appositive phrase can be removed from a sentence without changing its meaning or making it ambiguous:
Learning comma usage in English, a relatively boring topic, is helpful in producing clear texts.
An absolute phrase is treated as a parenthetical element:
Frankly, it doesn’t seem to matter to some people.
An addressed person’s (or people’s) name is always parenthetical:
I understand that, dear students, but proper comma usage really helps make your writing clearer.

11. The English House of Commas
Another parenthetical element:
An interjection is treated as a parenthetical element:
Excuse me, but there are, of course, many people who have other exams on that day. Can’t we reschedule the midterm, please?

12. The English House of Commas
One of the most important aspects of the “parenthetical element” discussion is the difference between “which” and “that”.
-> The book, which I bought yesterday, is interesting.
The basic sentence is “The book is interesting”. The “extra” (parenthetical) information “which I bought yesterday” is not “essential” to understand what the writer means.
-> The book that I bought yesterday is interesting.
In this sentence the writer makes it clear that a specific book is interesting.
A good explanation of this in German can be found here.
If you distinguish between “which” and “that” consistently in your writing (especially technical writing), it helps readers understand what is “essential” for them to know and what isn’t.

13. The English House of Commas
A special note for people who know German!
The structure “subject + verb + comma + Nebensatz”, which is very common in German, doesn’t exist in English.
Er sagte, dass … -> He said that (no comma!)
Sie meinte, dass … -> She thought that (no comma!)
Wir hoffen, dass … -> We hope that (no comma!)
Es ist zu erwarten, dass … -> It can be expected that (no comma!)

14. The English House of Commas
One last rule: Don’t over-use commas! When a comma is needed, use it; otherwise, do without.
Reviewing the rules of comma usage will help you understand the way sentences are built — and that, ultimately, will help you become a better writer.