A Dictionary of Law (9 ed. 2018). Edited by Jonathan Law. Quantum
quantum n. (of damages)
The amount of money awarded by way of damages.
damages pl. n.
A sum of money awarded by a court as compensation for a tort or a breach of contract. Damages are usually a lump-sum award (see also provisional damages). The general principle is that the claimant is entitled to full compensation (restitutio in integrum) for his losses. Substantial damages are given when actual damage has been caused, but nominal damages may be given for breach of contract and for some torts (such as trespass) in which no damage has been caused, in order to vindicate the claimant’s rights. Damages may be aggravated by the circumstances of the wrong. In exceptional cases in tort (but never in contract) exemplary damages may be given to punish the defendant’s wrongdoing. Damages may be classified as unliquidated or liquidated. Liquidated damages are a sum fixed in advance by the parties to a contract as the amount to be paid in the event of a breach. They are recoverable provided that the sum fixed was a fair pre-estimate of the likely consequences of a breach, but not if they were imposed as a penalty. Unliquidated damages are damages the amount of which is fixed by the court. Damages may also be classified as general and special damages.
I'll cite some uses of 'quantum'. Anson's Law of Contract (2016 30 ed) p 432.
Where the covenantee has a legitimate interest which it is entitled to protect, the restriction must not be longer in point of time, or wider in area, or otherwise be more extensive in scope than is necessary to protect that interest. The answer to this question in any individual case, however, must necessarily depend upon the interest to be protected, the nature of the contract and the relative positions of the contracting parties.159
The quantum of the consideration which the covenantor has received in exchange for the restraint is relevant to the determination of the reasonableness of the contract.160
Gardner has put forward the following ((1999) 115 LQR 438, 452) as a possible hypothesis for the remedial regime for proprietary estoppel:
The approach is – to vindicate the plaintiff’s expectations (care being taken to achieve the best match between the details of the plaintiff’s expectations and the possible legal responses);
– to vindicate those expectations in specie if practicable, but otherwise in a monetary form; but
– to resort to some other quantum, not more generous than the expectation measure, if it is impracticable to give relief in the expectation measure; and
– to resort to some other quantum, with no ceiling at the expectation measure, in the presence of another factor from a limited range recognised as meriting a departure from expectation relief.
p 608. Hoffmann LJ in William Sindall plc v. Cambridgeshire County Council  1 WLR 1016.
Damages under section 2(2) are therefore damages for the misrepresentation as such. What would be the measure of such damages? This court is not directly concerned with quantum, which would be determined at an inquiry.
pp 727-728. Robert Goff J.
In other cases, however, the actual benefit to the defendant may be considerably more than the appropriate or just sum to be awarded to the plaintiff, in which event the value of the benefit will not in fact determine the quantum of the award. I should add, however, that, in a case of prospecting, it would usually be wrong to identify the discovered mineral as the benefit.
p. 817. Lord Lloyd in Ruxley Electronics and Construction Ltd v. Forsyth  AC 344.
Mr Forsyth was, I think, lucky to have obtained so large an award for his disappointed expectations. But as there was no criticism from any quarter as to the quantum of the award as distinct from the underlying principle, it would not be right for your Lordships to interfere with the judge’s figure.