1A somewhat formal, written conjunction used to rephrase or clarify what was just said — 'that is', 'namely', 'i.e.'. Close in meaning to つまり but more formal.
この会社の売上は前年比で半減した。すなわち、経営は非常に厳しい状況にある。
This company's sales have halved year-on-year — that is, its management is in a very difficult situation.
彼は私の父の兄、すなわち伯父にあたる人だ。
He is my father's older brother, that is, my uncle.
水はH2O、すなわち水素原子2つと酸素原子1つからなる分子である。
Water is H2O — namely, a molecule made of two hydrogen atoms and one oxygen atom.
投票率は過去最低、すなわち有権者の関心が薄れていることを示している。
Voter turnout hit a record low — namely, it shows that voters' interest is fading.
2A more emphatic use meaning 'precisely' or 'exactly' — stressing that something is exactly, and nothing other than, what was stated.
彼の沈黙は、すなわち同意のしるしだった。
His silence was, precisely, a sign of agreement.
努力を怠らないこと、それがすなわち成功への道である。
Never neglecting one's effort — that, precisely, is the path to success.
3A somewhat archaic pattern, '〜ばすなわち...', indicating that what follows is the natural or inevitable consequence of what precedes. Rarely used in modern conversation.
春過ぎればすなわち夏が来る。
Once spring passes, then summer inevitably comes.