a Latin phrase meaning "mark well, observe particularly," 1721, from Latin nota, second person singular imperative of notare "to mark" (from nota "mark, sign, note, character, letter;" see note (n.)) + bene "well" (see bene-). Often abbreviated N.B.
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Definitions of n.b.
a Latin phrase (or its abbreviation) used to indicate that special attention should be paid to something;