Webster’s Revised Unabridged Dictionary · 1913
Quantum
Quan′tum (kwŏn′tŭm), n.; pl. Quanta (#). [L., neuter of quantus how great, how much. See Quantity,] 1. Quantity; amount. "Without authenticating . . . the quantum of the charges." Burke.
2. (Math.) A definite portion of a manifoldness, limited by a mark or by a boundary. W. K. Clifford.
Quantum meruit [L., as much as he merited] (Law), a count in an action grounded on a promise that the defendant would pay to the plaintiff for his service as much as he should deserve. — Quantum sufficit, or Quantum suff. [L., as much suffices] (Med.), a sufficient quantity. — Quantum valebat [L., as much at it was worth] (Law), a count in an action to recover of the defendant, for goods sold, as much as they were worth. Blackstone.