adjunct word
Linguistics term for a word that adds extra information to a sentence but is not grammatically essential.
"付加語" is a technical term used in linguistics.
In this sentence, the adverb functions as an adjunct word.
Compound of 付加 (fuka, 'addition') and 語 (go, 'word'). The exact historical derivation is uncertain, but the term is a modern linguistic coinage.