What is Average?

Legal Definition
In colloquial language, an average is the sum of a list of numbers divided by the number of numbers in the list. In mathematics and statistics, this would be called the arithmetic mean. In statistics, mean, median, and mode are all known as measures of central tendency.
-- Wikipedia
Legal Definition
A term used in commerce to signify a contribution made by the owners of the ship, freight and goods, on board, in proportion to their respective interests, towards any particular loss or expense sustained for the general safety of the ship and cargo; to the end that the particular loser may not be a greater sufferer than the owner of the ship and the other owners of goods on board. Marsh. Ins. B. 1, c. 12, s. 7; Code de Com. art. 397; 2 Hov. Supp. to Ves. jr. 407; Poth. Aver. art. Prel.

2. Average is called general or gross average, because it falls generally upon the whole or gross amount of the ship, freight and cargo; and also to distinguish it from what is often though improperly termed particular average, but which in truth means a particular or partial, and not a general loss; or has no affinity to average properly so called. Besides these there are other small charges, called petty or accustomed averages; such as pilotage, towage, light-money, beaconage, anchorage, bridge toll, quarantine, river charges, signals, instructions, castle money, pier money, digging the ship out of the ice, and the like.

3. A contribution upon general average can only be claimed in cases where, upon as much deliberate on and consultation between the captain and his officers as the occasion will admit of, it appears that the sacrifice at the time it was made, was absolutely and indispensably necessary for the preservation of the ship and cargo. To entitle the owner of the goods to an average contribution, the loss must evidently conduce to the preservation of the ship and the rest of the cargo; and it must appear that the ship and the rest of the cargo were in fact saved. Show. Ca. Parl. 20. See generally Code de Com. tit. 11 and 12; Park, Ins. c. 6; Marsh. Ins. B. 1, c. 12, s. 7 4 Mass. 548; 6 Mass. 125; 8 Mass. 467; 1 Caines' R. 196; 4 Dall. 459; 2 Binn. 547 4 Binn. 513; 2 Serg. & Rawle, 237, in note; 2 Serg. & Rawle, 229 3 Johns. Cas. 178; 1 Caines' R. 43; 2 Caines' R. 263; Id. 274; 8 Johns. R . 237, 2d edit 9 Johns. R. 9; 11 Johns. R 315 1 Caines' R. 573; 7 Johns R. 412; Wesk. Ins. tit. Average; 2 Barn. & Crest. 811 1 Rob. Adlm. Rep. 293; 2 New Rep. 378 18 Ves. 187; Lex. Mer. Armer. ch. 9; Bac Abr. Merchant, F; Vin. Abr. Contribution and' Average; Stev. on Av.; Ben. on Av.
-- Bouviers Law Dictionary
Legal Definition
A medium, a mean proportion. In old English law. A service by horse or carriage, anciently due by a tenant to his lord. Cowell. A labor or service performed with working cattle, horses, or oxen, or with wagons and carriages. Spelman. Stubble, or remainder of straw and grass left in cem-flelds utter harvest. In Kent it is called "gratten," and in other parts "roughings." In maritime law. Loss or damage accidentally happening to a vessel or to its cargo during a voyage. Also a small duty paid to masters of snips, when goods are sent in another man's ship, for their care of the goods, over and above the freight In marine insurance. Where loss or damage occurs to a vessel or its cargo at sea, average is the adjustment and apportionment of such loss between the owner, the freight, and the cargo, in proportion to their respective interests and losses, in order that one may not suffer the whole loss, but each contribute ratably. Coster v. Insurance Co., 2 Wash. C. C. 51, 6 Fed. Cas. 611; Insurance Co. v. Bland, 9 Dana (Ky.) 147; Whit-teridge v. Norris, 6 Mass. 125; Nickerson v. Tyson, 8 Mass. 467; Insurance Ch v. Jones, 2 Bin. (Pat) 552. It is of the following kinds: General average (also called "gross") consists of expense purposely incurred, sacrifice made, or damage sustained for the common safety of the vessel, freight, and cargo, or the two of them, at risk, and is to be contributed for by the several interests in the proportion of their respective values exposed to the common danger, and ultimately surviving, including the amount of expense, sacrifice, or damage so incurred in the contributory value. 2 Phll. Ins. ยง 1269 et seq. 2 Steph. Comm. 179; Padelford v. Board-man, 4 Mass. 548. Particular average is a loss happening to the ship, freight, or cargo which is not to be shared by contribution among all those interested, but must be borne by the owner of the subject to which it occurs. It is thus called in contradistinction to general average. Bargett v. Insutance Co., 3 Bosw. (N. Y.) 395. Petty average. In maritime law. A term used to denote such charges and disbursements as, according to occurrences and the custom of every place, the master necessarily furnishes for the benefit of the ship and cargo, either at the place of loading or unloading, or on the voyage; such as the hire of a pilot for conducting a vessel from one place to another, towage, light money, beaconage, anchorage, bridge toll, quarantine and such like. Park, Ins. 100. The partichlars belonging to this head depend, however, entirely upon usage. Abb. Ship. 404. Simple average. Particular average, (q. v.)
See also
-- Black's Law Dictionary
Legal Definition
Loss to a ship or cargo; apportionment of marine loss; sum paid to a master for caring for a cargo. See 2 Wash. C. C. 51, 6 Fed. Cas. (U. S.) 611.
-- Ballentine's Law Dictionary