Choose the correct part of speech of the underlined word

In the sentence "They arrived soon after," the word "soon" is an adverb.

Grammatical Analysis
To understand why, we look at the function of the word within the sentence:

Function: An adverb is a word that modifies a verb, an adjective, or another adverb. In this specific sentence, "soon" modifies the verb "arrived."

Question Answered: It answers the question "When did they arrive?" by providing temporal information about the action of arriving. Since it describes the timing of the verb "arrived," it is classified as an adverb.