noun, used as a prefix, noun
Used as a prefix or noun to indicate something is inverted, reversed, or contrary to the usual direction or order. Common in compounds like 逆さま (upside down) and 逆方向 (opposite direction).
その矢印は逆方向を指している。
The arrow points in the opposite direction.
彼は逆の意見を持っている。
He holds the opposite opinion.
逆さま specifically means 'upside down' or 'inverted', while 逆 is a broader prefix/noun for 'reverse' or 'opposite'.
反対 is a common noun/adjective meaning 'opposition' or 'contrary', often used in everyday speech. 逆 is more often used as a prefix in compounds.
The kanji 逆 means 'reverse' or 'invert'. The reading さか is a native Japanese reading (kun'yomi) associated with this meaning. The alternate form 倒 is rare and likely an ateji or variant usage.