An appositive is a noun or pronoun—often with modifiers—set beside another noun or pronoun to explain or identify it. Here are some examples of appositives. The appositive is in BOLD.
Your friend Bill is in trouble (friend is the noun, Bill is the appositive).
My brother’s car, a sporty red convertible, is the envy of my friends (brother’s car is the noun; sporty red convertible is the appositive).
A bold innovator, Wassily Kandinsky is known for his abstract paintings.
A beautiful collie, Skip was my favorite dog.
Punctuation of appositives:
In some cases, the noun being explained is too general without the appositive (i.e. the information is essential to the meaning of the sentence). When this is the case, DO NOT place commas around the appositive; just leave it alone. If the sentence would be clear and complete without the appositive, then commas are necessary; place one before and one after the appositive.
Here are some examples.
The popular US president John Kennedy was known for his eloquent and inspirational speeches.
(Without the appositive, the sentence would be The popular US president was known for his eloquent and inspirational speeches. We wouldn’t know which president was being referred to.)
John Kennedy, the popular US president, was known for his eloquent and inspirational speeches.
(Here we put commas around the appositive because it is not essential information. Without the appositive, the sentence would be John Kennedy was known for his eloquent and inspirational speeches. We still know who the subject of the sentence is without the appositive.)
John Kennedy the popular US president was quite different from John Kennedy the unfaithful husband.
(Here we do not put commas around either appositive because they are both essential to understanding the sentence. Without the appositives, the sentence would just be John Kennedy was quite different from John Kennedy. We wouldn’t know what qualities of John Kennedy were being referred to without the appositives.)
ONCE MORE, HERE ARE THE RULES: If it’s essential, leave it alone; if unessential, separate with commas!
What punctuation dilemmas or word usages cause you the greatest difficulty?