What Part Of Speech Is The Word Next Week?

'Next week', along with 'this year', 'yesterday,' 'tomorrow,' 'soon,' etc. Are all adverbs, because they add description to the verb of the sentence by indicating WHEN the action occurs.

"I ate it yesterday"
"I will go next week"
"You should leave soon"
"This year, I'm learning karate."

Note that they are not always adverbs, such as when preceded by a preposition (like "before next week") or are the subject of a verb (like "yesterday was awesome.")

Humm, I think "The Word" will be the same part of speech next week as it is this week.

Unless of course you mean the phrase "next week" in which "next" is an adjective by describing and modifying the noun "week"

"Next Week" is a phrase in simple future tense.