What is Betterment?

Legal Definition
Betterment, making better, is a general term used particularly in connection with the increased value given to real property by causes for which a tenant or the public, but not the owner, is responsible; it is thus of the nature of unearned increment. When, for instance, some public improvement results in raising the value of a piece of private land, and the owner is thereby bettered through no merit of his own, he gains by the betterment, and many economists and politicians have sought to arrange, by taxation or otherwise, that the increased value shall come into the pocket of the public rather than into the owner's. A betterment tax would be assessed in order to divert from the owner of the property the profit thus accruing unearned to him. The whole problem is one of the incidence of taxation and the question of land values, and various applications of the principle of betterment have been tried in the United States and in England, raising considerable controversy from time to time.
-- Wikipedia
Legal Definition
Improvement's made to an estate. It signifies such improvements as have been made to the estate which render it better than mere repairs. See 2 Fairf. 482; 9 Shepl. 110; 10 Shepl. 192; 13 Ohio, R. 308; 10 Yerg. Verm. 533; 17 Verm. 109.
-- Bouviers Law Dictionary
Legal Definition
An improvement put upon an estate which enhances Its value more than mere repairs. The term ls also applied to denote the additional value which an estate acquires in consequence of some public improvement, as laying ont or widening a street, etc. French v. New York, 16 How. Prae. (N. Y.) 220; Abell v. Brady, 79 Md. 94, 28 Atl. 817; Chase v. Sioux City, 86 Iowa, 603, 53 N. W. 333. See Betterment acts.
-- Black's Law Dictionary
Legal Definition
A asset whose changes are made to make services better.
Legal Definition
Improvements beyond upkeep. See 81 Am. St. Rep. 164.
-- Ballentine's Law Dictionary