Used to express strong conviction or agreement, often in response to a statement or when confirming something one has heard or experienced.
That's certainly a good idea.
It's true the price is high, but the quality is very good.
What he says is surely correct.
He definitely said that.
I definitely saw him there.
きっと expresses the speaker's confident guess or prediction about something uncertain, while 確かに confirms something already known or observed.
もちろん readily agrees with an obvious point ('of course'), whereas 確かに acknowledges the truth of a statement, often before adding a qualification.
確かに is the everyday modern word for 'certainly', while 定 (さだ) is an archaic adverb rarely used outside classical or poetic texts.
確かに confirms that something is certainly true, while 正に emphasizes that it is exactly or precisely so, often with more rhetorical force.
確かに emphasizes agreement with the truth of a statement, whereas なるほど focuses on the moment of understanding why something is so.
確かに expresses certainty based on evidence or memory, while まさしく conveys a more emphatic, subjective sense of 'indeed' or 'exactly'.
確かに is the standard modern adverb for 'certainly/surely', whereas 一定 is an old-fashioned equivalent used mainly in classical or emphatic speech.
確か is a na-adjective meaning 'certain' or 'reliable' (as in 確かな情報), while 確かに is its adverbial form meaning 'surely' or 'certainly'.
Standard kanji spelling.
Rarely used kanji form.
Adverbial form of the na-adjective 確か (certain).