ref – https://blog.prepscholar.com/what-part-of-speech-is-the-word-the

the is classified as an article, which is a word used to define a noun.

When ‘the’ is functioning as an adjective, it comes before a noun in order to clarify/describe whether it’s specific or non-specific.

However, the can also sometimes function as an adverb in certain instances, too.

“the” is an article that functions as both an adjective and an adverb, depending on how it’s being used.
In other words, it’s an article, adjective, and an adverb!

definite articile

The word ‘the’ is considered a definite article because it defines the meaning of a noun as one particular thing.

We went to the rodeo on Saturday. Did you see the cowboy get trampled by the bull?

This sentence has three instances of “the” functioning as a definite article:

the rodeo,
the cowboy,
the bull.

Notice that in each instance, ‘the’ comes directly before the noun. That’s because it’s an article’s job to identify nouns.

In each of these three instances, ‘the’ refers to a specific (or definite) person, place, or thing.

When the speaker says the rodeo, they’re talking about one specific rodeo that happened at a certain place and time.

The same goes for the cowboy and the bull: these are two specific people/animals that had one kinda terrible thing happen to them!

indefinite article

It can be a bit easier to see how definite articles work if you see them in the same sentence as an indefinite article (a or an).
This sentence makes the difference a lot more clear:

A bat flew into the restaurant and made people panic.

Okay. This sentence has two articles in it: a and the. So what’s the difference?

Well, you use ‘a’ when you’re referring to a general, non-specific person, place, or thing because its an indefinite article. So in this case, using ‘a’ tells us this isn’t a specific bat. It’s just a random bat from the wild that decided to go on an adventure.

Notice that in the example, the writer uses ‘the’ to refer to the restaurant. That’s because the event happened at a specific place.

A bat flew into one particular restaurant to cause havoc, which is why it’s referred to as the restaurant in the sentence.

‘The’ as an Adverb

Finally, we mentioned that ‘the’ can also be used as an adverb, which is one of the eight main parts of speech. Adverbs modify or describe verbs, adjectives, or other adverbs, but never modify nouns.

Sometimes, ‘the’ can be used to modify adverbs or adjectives that occur in the comparative degree. Adverbs or adjectives that compare the amounts or intensity of a feeling, state of being, or action characterizing two or more things are in the comparative degree. Sometimes ‘the’ appears before these adverbs or adjectives to help convey the comparison!

Here’s an example where ‘the’ functions as an adverb instead of an article/adjective:

Lainey believes the most outrageous things.

Okay. We know that when ‘the’ is functioning as an adjective, it comes before a noun in order to clarify whether it’s specific or non-specific.

In this case, however, ‘the’ precedes the word most, which isn’t a noun, it’s an adjective.

And since an adverb modifies an adjective, adverb, or verb, that means ‘the’ functions as an adverb in this sentence.

Giovanni’s is the best pizza place in Montana.

The trick to figuring out whether the article ‘the’ is functioning as an adjective or an adverb is pretty simple:

just look at the word directly after ‘the’ and figure out its part of speech.

If that word is a noun, then the is functioning as an adjective.

If that word isn’t a noun, then the is functioning like an adverb.

Comparisons

Remember how we explained that ‘the’ can be combined with adverbs that are making a comparison of levels or amounts of something between two entities? The example above shows how the can be combined with an adverb in such a situation. The is combined with more and likely to form an adverbial phrase.

So how do you figure this out? Well, if the words immediately after the are adverbs, then the is functioning as an adverb, too!

Here’s another example of how the can be used as an adverb:

I had the worst day ever.

In this case, ‘the’ is being combined with the adverb worst to compare the speaker’s day to the other days. Compared to all the other days ever, this person’s was the worst…period. Some other examples of adverbs that you might see the combined with include all the better, the best, the bigger, the shorter, and all the sooner.

You are the best!

He’s the worst player I have ever seen.