Alfred, King of England, resisted the Danes.

“King of England” is in apposition to “Alfred.”

Two nouns side by side, where one modifies the other, seems an incomplete definition. For example: “I have a television screen.” This has two nouns side by side (i.e., television screen), and “television” describes “screen.” Would this, then, be an appositive?

Let’s look at two examples of appositives taken from the Online Writing Lab at Perdue (http://owl.english.purdue.edu/owl/resource/596/1)

1. “My brother’s car, a sporty red convertible with bucket seats, is the envy of my friends.”

The appositive is “a sporty red convertible with bucket seats.” This is an appositive for “car.” Let’s see what this appositive is doing.
First, it is defining and/or modifying “car.” It is renaming “car” inasmuch as it means the same thing. Car = a sporty red convertible with bucket seats.

Second, it can serve the same grammatical function. In this sentence, “My brother’s car” is the subject. However, if we remove the subject (and fix the punctuation), “A sporty red convertible with bucket seats” becomes the subject. [This one is non-restrictive. My brother has only one car. As such, the appositive is set off with commas.]

2. Your friend Bill is in trouble.

“Bill” is an appositive for “friend.” “Bill” is renaming “friend” inasmuch as it means the same thing. Friend = Bill. Second, the appositive can serve the same grammatical function. The sentence “Your friend is in trouble” has the same grammatical structure as “Bill is in trouble.” [This one is restrictive, assuming you have more than one friend. As such, the appositive is not set off with commas.]

Perhaps the confusion comes from the part of your definition for appositive: “defines or modifies.” “Modify” does not mean as “define.” The Center for Writing Studies at the University of Illinois (http://www.cws.illinois.edu/wo.....positives/) provides a decent definition: Appositives are two words or word groups which MEAN THE SAME THING and are placed together. Appositives identify or explain the nouns or pronouns which they modify.

Here is one of their examples: “Our teacher, Professor Lamanna, loves grammar.” The appositive they identify is “Professor Lamanna.” This appositive renames “our teacher” and can serve as the same grammatical function if “our teacher” (and the pair of commas) is removed.

What does this mean? To determine whether or not a word or words are appositives, we need to look at what they are doing and how they are used.

Now let’s look at “writers conference,” which you say is an appositive in “Are you planning to go to a writers conference?” Because you compare “writers” to “writers’,” I’m assuming you mean “writers” is the appositive. Here, the noun “writers” is side by side with “conference,” and it describes or modifies “conference.” Let’s see if “writers” works the same way as the appositives above.

First, does “writers” rename, restate, or define “conference”? Does “writers” = “conference.” No. It does modify or describe it. In this way, it is serving as an adjective.

Second, can “writers” and “conference” serve the same function in the sentence? Can we say “go to a writers” and “go to a conference”? Again, no.

(If you meant “conference” to be the appositive, we can apply the same evaluation–with the same result.)

But, as I mentioned above, I hope Maeve will toss in her two cents.