In the sentence "Let's walk around.", is around a noun? Also, in the sentence "Let's walk around the block.", what part of speech is around?

Many words can be identified as adverbs AND prepositions, depending on how they're used in the sentence.

In your first sentence, "around" is an adverb. It's telling where the verb is taking place.

In the second sentence, "around" is a preposition; the entire prepositional phrase is "around the block" and it's being used adverbially.

http://grammar.ccc.commnet.edu/grammar/adverbs.htm

http://grammar.ccc.commnet.edu/grammar/prepositions.htm

No, "around" tells where you are walking, so it modifies the verb.

"Around the block" is a prepositional phrase telling where you are walking.... so around is a what ?

In the sentence "Let's walk around.", the word "around" is not a noun. It is an adverb modifying the verb "walk." An adverb is a part of speech that provides extra information about a verb, an adjective, or another adverb.

In the sentence "Let's walk around the block.", the word "around" is also an adverb. It modifies the verb "walk" and indicates the direction or manner in which someone is walking.

In the sentence "Let's walk around.", the word "around" is not a noun. It is actually functioning as an adverb in this context. Adverbs often modify verbs, and in this case, "around" specifies the direction or manner of the walking.

To determine the part of speech of a word, you can look at how it is used in the sentence and its function within the sentence structure. In this particular sentence, "around" does not serve as a noun because it does not represent a person, place, thing, or idea.

Now, let's analyze the second sentence: "Let's walk around the block." In this case, "around" is still functioning as an adverb, modifying the verb "walk." It provides additional information about the type or direction of movement. "The block," on the other hand, is a noun phrase, functioning as an object of the preposition "around." It represents a specific place or thing (the block) that is being referred to.

To identify the part of speech of a word, it is crucial to consider how it is used within the specific sentence and its role in conveying meaning.