definitely

確かに；間違いなく；（返答で）もちろん；絶対に

入試の言い換え

• certainly 確かに；もちろん — 丁寧で落ち着いた言い方
• absolutely まったくその通り；絶対に — 返答の強い同意にも
• surely きっと — 話し手の確信・期待（驚きを含むことも）
• without doubt 疑いなく — 書き言葉でも使える
• undoubtedly 疑いなく — 硬め
• for sure 確実に — 口語
• by all means ぜひどうぞ — 許可・勧誘への返答の意味で

会話で Are you coming? — Definitely! のように一語で「もちろん！」になる便利な副詞。確信度のはしごは definitely > probably > maybe / perhaps > possibly。英作文で確信度を正確に書き分けると論理の説得力が上がる。

definitely の類語

certainly, absolutely, surely, without doubt, undoubtedly, for sure, by all means, unquestionably, distinctly, indeed, exactly, expressly, clearly, by all odds, decidedly, precisely, emphatically, assuredly, in spades, really, literally, truly, obviously, to be sure, explicitly, strictly, to the letter, positively, evidently, just, simply, especially, even, right, quite, straight, dead, faithfully, particularly, directly, square, plainly, apparently, noticeably, specifically, unerringly, doubtless, of course, for a fact, patently, explicit, for certain, point-blank, certainty, nothing else but, manifestly, separately, at any rate, in particular, word for word

definitely の反意語

maybe, possibly, definitely not

例文

• If you don't study harder, you'll definitely fail.
  もっと勉強しないときっと失敗するわよ。
• I definitely wouldn't go there by myself.
  そこへ決して一人で行かない。
• Lucy will definitely get married to the pop singer.
  ルーシーが流行歌手と結婚するのは確かだ。

definitely の言い換えを探すには

definitely（確かに）の類語・言い換え（パラフレーズ）を、日本語訳つきで関連度順に並べています。入試で狙われる言い換えパターン、ニュアンスの違い、語源、日本人がやりがちなワナも解説。英作文の語彙を増やしたいとき、長文読解で本文と選択肢の言い換えを見抜きたいときに使えます。