Waiver has often been used in senses synonymous with election or estoppel. It has been suggested (see, eg, Finagrain SA Geneva v P Kruse Hamburg [1976] 2 Lloyd's Rep 508 at 534 per Megaw LJ) that waiver is indistinguishable from one or other of those doctrines. Sometimes, although expressed in terms of waiver, the reasoning adopted in cases reveals the elements for applying a more specific principle, typically election (see, eg, R v Paulson [1921] 1 AC 271 at 280, 283; Motor Oil Hellas (Corinth) Refineries SA v Shipping Corporation of India (The Kanchenjunga) [1990] 1 Lloyd's Rep 391 at 397-398) or estoppel (see, eg, Enrico Furst & Co v WE Fischer Ltd [1960] 2 Lloyd's Rep 340 at 349-350; W J Alan & Co Ltd v El Nasr Export & Import Co [1972] EWCA Civ 12; [1972] 2 QB 189 at 213). And it may be that in cases of the several kinds last mentioned, the term is used as no more than a conclusionary word stating the consequences of the operation of that more specific principle, rather than as indicating the application of any distinct and independent principle.
Nonetheless, it is clear that there are cases in which the word has been used in senses other than those embraced by principles of election, estoppel or variation of contract. So, for example, waiver has been used in the sense of rescission where what has occurred is 'an entire abandonment and dissolution of the contract' (Mulcahy v Hoyne [1925] HCA 17; (1925) 36 CLR 41 at 53 per Isaacs J, citing Price v Dyer [1810] EngR 588; (1810) 17 Ves Jr 356 at 364 [34 ER 137 at 140]). It has been used in connection with a party not insisting upon a term of a contract which is identified as a term for that party's sole benefit (see, eg, Mulcahy v Hoyne [1925] HCA 17; (1925) 36 CLR 41 at 55 per Isaacs J; at 58 per Starke J; Gange v Sullivan [1966] HCA 55; (1966) 116 CLR 418 at 429 per Barwick CJ). And from time to time 'waiver' has been used (see, eg, Bacon v Purcell [1916] UKPCHCA 2; (1916) 22 CLR 307 at 312; Embrey v Earp (1890) 6 WN (NSW) 130 at 131) to describe some modification of the terms of a contract without the formalities, or consideration, necessary for an effective contractual variation.
The uncertainties and difficulties which attach to the use of the term 'waiver' have been recognised in judgments of this court (see, eg, The Commonwealth v Verwayen (1990) 170 CLR 394 at 406 per Mason CJ; at 422 per Brennan J; at 467, 472 per Toohey J; Mann v Carnell [1999] HCA 66; (1999) 201 CLR 1 at 13 [28] per Gleeson CJ, Gaudron, Gummow and Callinan JJ). Yet 'waiver' remains firmly embedded in the lawyer's lexicon. For example, in Osland v Secretary to the Department of Justice (2008) 234 CLR 275 this court considered the circumstances in which by its conduct a party entitled to legal professional privilege against the production of documents is to be taken to have 'waived' that privilege ((2008) 234 CLR 275 at 296-297 [45], 298-299 [49], 312-313 [97], 321 [131]).
The uncertainties and difficulties which attach to the use of the term have prompted attempts to construct a taxonomy of waiver in which distinctions are drawn between 'waiver by election' and 'pure waiver' (Wilken and Villiers, The Law of Waiver, Variation and Estoppel, 2nd ed (2002), pp 45-46 [4.01], 60 [4.28]) or between 'waiver by election' and 'unilateral waiver' (Glencore Grain Ltd v Flacker Shipping Ltd (The Happy Day) [2002] EWCA Civ 1068; [2002] 2 Lloyd's Rep 487 at 506 [64] per Potter LJ). It is not necessary to consider whether such classifications are useful. Rather, it is important to identify the principles that are said to be engaged in the particular case [51] - [54].