In the phrase "the day that we met each other," the word "that" functions as a relative pronoun, not a relative adverb.

Here’s why:

1. Relative Pronoun: In this context, "that" refers to "the day" and introduces the clause "we met each other." It functions to link the noun "day" to additional information about what happened on that day (the meeting). Although the clause "we met each other" is complete, "that" here serves as a connector referring back to "the day."

2. Relative Adverbs: Relative adverbs, such as "when," "where," and "why," usually modify the time, place, or reason of the noun. If we used "when" instead, as in "the day when we met each other," it would serve as a relative adverb indicating a specific time.

In short, "that" in this sentence is a relative pronoun because it refers to "the day" rather than modifying it in terms of time, place, or reason.

한국에서는 저거 관계부사 when 대신에 쓴거라 관계부사 대용 that이라고 부른다