What is the rule regarding using the with superlatives? For example:
- John is the fastest among his friends.
- John is fastest among his friends.
Both appear to be correct. I have seen both formats in a variety of places.
Both are indeed correct. An article is only necessary in the superlative (or comparative) if the adjective is attributive (i.e. is in the same phrase as the noun it is describing).
Consider the following examples:
As is shown in the examples above, omitting the in #1 causes it to become ungrammatical, as the superlative fastest is in the same phrase as its noun boy. In #2, however, the may be freely omitted as it is not attributive.
Some English superlatives, however, use the adverb most, which can cause some amount of confusion. Consider the following examples:
All three of these examples are grammatical and show the overlap of an adverbial intensification with the superlative. With the definite article the, it can only be a superlative, but with the indefinite article a it can only be interpreted adverbially (i.e. essentially the same as "very beautiful"). Both of these forms, however, allow omission of the article, and so the meaning of #2 is left ambiguous.
Note that there is a third form which is related to the superlative known as the elative. While it is not a separate inflection, it can be shown to exist in constructions such as the following:
This sentence is generally understood not to mean with a pleasure greater than any other, but rather something more akin to with extreme pleasure.
Both are correct, but have subtly different meanings. If I can use a different example, perhaps it will explain:
In the first sentence it means that compared to his friends John is the most talkative of them all, none of them talk as much as John does. This is a superlative.
In the second it indicates that when he is amongst his friends John is at his most talkative, but without his friends, perhaps his shyness kicks in, and he becomes much quieter.
The same applies in your example, but it is easier to see in the examples I gave. In your second sentence perhaps John runs in a race fastest when he is surrounded by his friends giving him encouragement, but that doesn't mean that his friends don't zoom past him to the finish line. However, in the first sentence, encouragement or not, John is crossing the finish line first.
I don't know of a study that's looked at this formally, so I'm going "off the top of my head". It seems to me that the difference is that if you say "David is fastest", you are implying that David is the fastest among the small group of people that you have seen, but implying that it is likely you would find somebody faster in the wider world. If you say "David is the fastest", you are slightly more implying "He is the fastest among this group and also is not likely to be beaten easily by other people".
Omitting "the" seems slightly more informal as well, to my UK ear.