adverb
Refers to the manner or state understood from context or the listener's words. Often used with a negative to mean 'not as much as one might think'.
そう言われても、どうすればいいかわからない。
Even if you say so, I don't know what to do.
He won't give up that easily.
interjection
yes; that's right; so it is
Interjection expressing agreement with what was just said.
「明日は休みだよね？」「そう。」
"Tomorrow is a holiday, right?" "Yes."
interjection
Interjection expressing doubt or seeking confirmation, often with rising intonation.
「彼、結婚するんだって。」「そう？」
"I heard he's getting married." "Really?"
Refers to something close to the speaker or in the speaker's manner, while そう refers to the listener's context or what was just mentioned.
Refers to something distant from both speaker and listener, or known to both, while そう is tied to the immediate conversational context.
Interrogative 'how' or 'in what way', while そう is the corresponding demonstrative 'in that way'.
Derived from the demonstrative root そ (so) with the adverbial suffix う (u). The kanji 然 is an ateji used for its meaning, but the word is native Japanese.