語源辞典
https://www.etymonline.com/word/adverb#etymonline_v_5160
で adverb (副詞)を引くと,
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"one of the indeclinable parts of speech, so called from being ordinarily joined to verbs for the purpose of limiting or extending their signification, but used also to qualify adjectives and other adverbs" [Century Dictionary], late 14c., from Late Latin adverbium "adverb," literally "that which is added to a verb" (to extend or limit its meaning), from ad "to" (see ad-) + verbum "verb, word" (from PIE root *were- (3) "to speak;" see verb). Coined by Flavius Sosipater Charisius as a translation of Greek epirrhema "adverb," from epi- "upon, on" + rhema "verb."
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もともとギリシャ語で「動詞 (rhema) に添える(epi)」という言葉epirrhema があり,これがラテン語に訳されて adverbium となる。
さらにこれを,英語に「ad+verb」のかたちで借用したようです。おおざっぱにいうと。
なお,副詞は,動詞のほかに形容詞や他の副詞にもつきます。
お礼
知らないのになぜ解答しようとするのでしょうか