Punctuation of Appositives
An appositive is a noun or pronoun (perhaps with some adjectives, etc.) which adds extra information to clarify a noun in the sentence. Take this sentence, for instance: My mom Angela is a good cook. Angela is the appositive for mom. If the appositive is not necessary to understand the sentence, there should be commas around the appositive. If the appositive is necessary to understand the sentence, don’t put commas around it.
A brilliant young painter, the artist was given his own show at the age of 19.
The appositive a brilliant young painter isn’t required to understand this sentence; there should be a comma after painter (but not at the beginning of the appositive, as it is at the beginning of the sentence).
The rose, a deep red blood drop, stood out amongst the tiny white flowers.
Martha, yawning with exhaustion, sat down at her desk to finish her last paper.
The professor, Dr. Kendrick, was a wonderful teacher.
The appositive Dr. Kendrick, is necessary in order to understand which professor was a wonderful teacher, so there is no need for commas around it.
Please hand me the paper, that is on the table.
The red car, with the flat tire, is pulled over to the side of the road.