rearr

Rearr is an abbreviation commonly used in scholarly writing to denote a rearrangement, or reorganization, of components within a system. It is not a standalone concept with a formal definition, but a shorthand that appears across disciplines to indicate that a process or step changes the arrangement of parts rather than adding or removing them. The term is most often found in older or more compact notation, and in contexts where space or clarity favors brief labeling.

In chemistry, rearrangements describe processes in which a molecule’s skeleton or substituent positions reorganize during a reaction. This can involve shifts of carbon skeletons, migration of groups, or changes in bonding patterns that yield a new isomer or structural framework without changing the overall molecular formula. Well-known examples include various rearrangement reactions that alter connectivity, such as Wagner-Meerwein and pinacol-type rearrangements. In reaction schemes and mechanistic discussions, a label like rearr. or rearrangement may be used to indicate that such a bond- or group-reorganization step occurs at that stage.

In mathematics and related fields, rearrangement refers to permuting the order of elements in a sequence or series, with associated concepts such as rearrangement inequalities or rearrangement theorems. In these contexts, rearr is sometimes used in notes or shorthand to indicate a step that reorders terms, rather than a critique of the underlying theory.

See also: rearrangement, rearrangement inequality, skeletal rearrangement.