LATIN DICTIONARYLexicon Latīnum
adverb

quamdiū

quamdiū (not comparable)
Classical[ˈkʷan.di.uː]Ecclesiastical[ˈkʷan.di.u]

Meaning

  1. not comparablehow long
    Seneca Minor, Epistulae Morales ad Lucilium, Epistle CIHow well you live, not how long.
  2. not comparableas long as, until, during
    Quamdiū mihi cōnsulī dēsignātō, Catilīna, īnsidiātus es, nōn pūblicō mē praesidiō sed prīvātā dīligentiā dēfendī.As long as I was consult-elect, Catiline, you plotted against me, [and] I defended myself not with a public guard but by private precautions.63 BCE, Cicero, In Catilinam orationes 1.11

quam-dĭu, less freq. quandĭu (mostly as two words, sometimes separated:
I. quam voluit diu, Cic. Q. Fr. 1, 1, 7), adv.
I. Interrog., how long ago? how long? quamdiu id factum est? Plaut. Capt. 5, 3, 3: quandiu apud vos ero, Vulg. Marc. 9, 18.—
II. Rel.
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.—
(b). 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. Of inference, inasmuch as, in that (late Lat.): quandiu fecistis uni ex his fratribus, Vulg. Matt. 25, 40.

Origins

Compound of quam (“how”) + diū (“long”)

Quick answers

What does quamdiū mean in Latin?
quamdiū, a adverb, means “how long; as long as, until, during”.
How do you pronounce quamdiū?
In classical Latin, [ˈkʷan.di.uː]; in ecclesiastical (church) Latin, [ˈkʷan.di.u].