"He ran the fastest." 'the fastest' is an adverb here, not a noun, so why does it use the definite article 'the'?
We could say "He ran fastest", and that works fine too.
If we say "He is the fastest runner", 'the' relates to the noun 'runner', so there is no problem–so the fact that superlative adjectives also have 'the' in front is not an issue…
But if we say "He is the fastest", is 'fastest': 1. a noun? 2. a predicate adjective, in which case why does it take 'the'? 3. an adverb–which is odd, because it would translate like 'He exists the fastest'? But then, you can also say "He is fastest".
There would seem to be some serious blurring and confusion here between 'the fastest' as a noun, an adjective and an adverb. "He is the fastest runner", "He is the fastest", "He ran the fastest", "He ran fastest", "He is fastest".
Best Answer
Collins Cobuild English Guides [3] ... Articles has the following to say:
Deletions follow different patterns, and quite often leave relicts whose part-of-speech is perhaps best classed as 'ex-adjective' etc (if one insists on assigning everything a POS):
She is the fastest runner.
She is the fastest.
She is fastest.
Sometimes, the definite article must be included:
She is the fastest I have seen.
...
A complication may be thought to arise when adverbs take the same form as adjectives:
She ran [the] fastest [of all the competitors].
She ran the fastest {cf faster than} I've ever seen her run.
However, this is a standard usage of the definite article, as seen with an ly-form adverb:
She ran the most smoothly [of all the competitors].
contrast the adverb-modifier usage:
She ran most [= extremely] smoothly.