- and
- or
- nor
- so
- but
- for
- yet
For example, the following is incorrect because the word "and" is connecting the nouns "John" and "Joe" which are nouns not independent clauses.
INCORRECT: John, and Joe, went to the mall.
Instead, the following is correct:
CORRECT: John and Joe went to the mall.
The word "John" would not be a sentence on its own; it's just a noun, and the word "Joe" is also just a noun. So the conjunction "and" in the two examples above is connecting two nouns, not two independent clauses. Therefore, a comma is not be used.
Here are some more examples:
INCORRECT: The furry, and big cat is named Paul.
CORRECT: The furry and big cat is named Paul.
The coordinating conjunction (the word "and") in the above examples is connecting the word "furry" with the word "big". The word "furry" is an adjective, not an independent clause. The word "big" is an adjective, not an independent clause. Therefore, in the examples above, the conjunction "and" is connecting two adjectives, not two independent clauses. Therefore, a comma must not be used.
INCORRECT: Jennifer wrote, and directed the show.
CORRECT: Jennifer wrote and directed the show.
In the above examples, the conjunction joins the verb "wrote" and and the verb "directed". Since it connects two verbs, not two independent clauses, a comma must not be used.
INCORRECT: Jennifer wrote the play, and directed the show.
CORRECT: Jennifer wrote the play and directed the show.
In the above example, the conjunction joins the phrase "wrote the play" and the phrase "directed the show". The phrase "directed the show" is not an independent clause. Therefore, a comma must not be used.
CORRECT: I went to the kitchen, and I ate pizza.
USUALLY INCORRECT: I went to the kitchen and I ate pizza. (Because this is only usually incorrect, it is NOT to be marked as an error in the objective section when editing reviews.)
In the above example, the conjunction joins the independent clause "I went to the kitchen" with the independent clause "I ate pizza". Therefore, generally a comma must be used. However, some style guides allow for the comma to be omitted if the two independent clauses are "very short". Because there is subjectivity in what qualifies as "very short", I recommend never mark the omission of this particular comma (one before a coordinating conjunction connecting two independent clauses) as an objective error, even if the sentences seem long. What is short, medium, or long can be subjective.
In the above examples, I used the conjunction "and". However, the same goes for other conjunctions. Here are more examples:
INCORRECT: The furry, but big cat is named Paul.
CORRECT: The furry but big cat is named Paul.
INCORRECT: Jennifer wrote, or directed the show.
CORRECT: Jennifer wrote or directed the show.
USUALLY INCORRECT: I went to the kitchen but I ate pizza.
CORRECT: I went to the kitchen, but I ate pizza.
Keep in mind, the above rules apply when dealing with a coordinating conjunction that connects two and only two equal parts. If three or more parts are connected, then a list is created and commas do become required. Here are some examples:
INCORRECT: The dog is big furry and mean.
CORRECT: The dog is big, furry, and mean.
ALSO CORRECT: The dog is big, furry and mean.
The optional comma left out in the very last example is called the Oxford Comma. Some style guides require it, but other style guides allow it to be left out. However, that is a different topic.
Sources and Additional Reading
https://writing.wisc.edu/Handbook/CoordConj.html
https://webapps.towson.edu/ows/conjunctions.htm
https://guidetogrammar.org/grammar/conjunctions.htm
http://plato.algonquincollege.com/appli ... age_id=156