Lewis & Short

quam-dĭu, less freq. quandĭu (mostly as two words, sometimes separated: quam voluit diu, Cic. Q. Fr. 1, 1, 7), adv.

  1. I. Interrog., how long ago? how long? quamdiu id factum est? Plaut. Capt. 5, 3, 3: quandiu apud vos ero, Vulg. Marc. 9, 18.
  2. II. Rel.
      1. 1. Of time, as long as, until, during (class.): quamdiu potuit, tacuit, Caes. B. G. 1, 17: disces, quamdiu voles, Cic. Off. 1, 1, 2; Col. 12, 52, 13.
          1. (β) Until (very rare): jubebat, ut semper id comesset, quamdiu tamen melius invenisset, Lampr. Elag. 29, 7.
            Comp.: quamdiutius, Not. Tir. p. 35.
            Sup.: ‡ quamdiutissime, Not. Tir. p. 35.
      2. 2. Of inference, inasmuch as, in that (late Lat.): quandiu fecistis uni ex his fratribus, Vulg. Matt. 25, 40.