In 1806, Jean-Robert Argand introduced the term module, meaning unit of measure in French, specifically for the complex absolute value,[REF][REF] and it was borrowed into English in 1866 as the Latin equivalent modulus [REF].
The vertical bar notation also appears in a number of other mathematical contexts: for example, when applied to a set, it is used to denote its cardinality; when applied to a matrix, it is used to denote its determinant.