(countable and uncountable, plural algebras)
- (uncountable, medicine, historical, rare) The surgical treatment of a dislocated or fractured bone. Also (countable): a dislocation or fracture.
- (uncountable, mathematics) A system for computation using letters or other symbols to represent numbers, with rules for manipulating these symbols.
- (uncountable, mathematics) The study of algebraic structures.
- (countable, mathematics) A universal algebra.
- (countable, algebra) An algebraic structure consisting of a module of a commutative ring along with an additional binary operation that is bilinear.
- (countable, set theory, analysis) A collection of subsets of a given set, such that this collection contains the empty set, and the collection is closed under unions and complements (thereby also under intersections and differences).
- (countable, mathematics) One of several other types of mathematical structure.
- (figuratively) A system or process, that is like algebra by substituting one thing for another, or in using signs, symbols, etc., to represent concepts or ideas.
From Medieval Latin, from Arabic word الجبر (al-jabr, “reunion, resetting of broken parts”) in the title of al-Khwarizmi's influential work الكتاب المختصر في حساب الجبر والمقابلة (al-kitāb al-muxtaṣar fī ḥisāb al-jabr wa-l-muqābala, “The Compendious Book on Calculation by Completion and Balancing”).