equity - In England (hence in Ireland and the United States), the distinctive name of a system of law existing side by side with the common and statute law (together called 'law' in a narrower sense), and superseding these, when they conflict with it.
The original notion was 'the recourse to general principles of justice', a decision 'in equity' being understood to be one given in accordance with natural justice, in a case for which the law did not provide adequate  remedy, or in which its operation would have been unfair. These decisions, however, were taken as precedents, and thus 'equity' early became an organized system of rules, not less definite and rigid than those of 'law'; though the older notion long continued to survive in the language of legal writers, and to some extent to influence the  practice of equity judges. In England, equity was formerly administered by a special class of tribunals, of which the Court of Chancery was chief; but since 1873 all the branches of the High Court administer both 'law' and 'equity', it being provided that where the two differ, the rules of equity are to be followed. Nevertheless, the class of cases formerly dealt with by the Court of Chancery are still reserved to the Chancery Division of the High Court.