Nabla symbol
From Wikipedia, the free encyclopedia
Nabla is the symbol 
(∇). The name comes from the Greek word for a Hebrew harp, which had a similar shape. Related words also exist in Aramaic and Hebrew. The symbol was first used by William Rowan Hamilton in the form of a sideways wedge: ⊳. Another, less-common name for the symbol is atled (delta spelled backwards), because the nabla is an inverted Greek letter delta. In actual Greek usage, the symbol is called ανάδελτα, anádelta, which means "upside-down delta".
The nabla symbol is available in standard HTML as ∇ and in LaTeX as \nabla. In Unicode, it is the character at code point U+2207, or 8711 in decimal notation.
Contents |
[edit] Use in mathematics
Nabla is used in mathematics to denote the del operator. It also can refer to a connection in differential geometry, as well as the all relation (most commonly in lattice theory). It was introduced by the Irish mathematician and physicist William Rowan Hamilton in 1837 [1]. William Thomson wrote in 1884: "I took the liberty of asking Professor Bell whether he had a name for this symbol and he has mentioned to me nabla, a humorous suggestion of Maxwell's. It is the name of an Egyptian harp, which was of that shape".[2]
In 1901, Josiah Willard Gibbs and Edwin Bidwell Wilson wrote: "This symbolic operator was introduced by Sir W. R. Hamilton and is now in universal employment. There seems, however, to be no universally recognized name for it, although owing to the frequent occurrence of the symbol some name is a practical necessity. It has been found by experience that the monosyllable del is so short and easy to pronounce that even in complicated formulae in which occurs a number of times no inconvenience to the speaker or listener arises from the repetition. V is read simply as 'del V' ".[3]
Nabla (instrument), a Hebrew stringed instrument also called a "Nebel"
[edit] See also
- Del, the vector differential operator
- Del in cylindrical and spherical coordinates
- grad, div, and curl, differential operators defined using del
- the Covariant derivative, a separate (and tensorial) differential operator defined for tensors
[edit] Footnotes
- ^ W. R. Hamilton, in Trans. R. Irish Acad. XVII. 236 (1837)
- ^ W. Thomson, Notes Lect. Molecular Dynamics & Wave Theory of Light at Johns Hopkins Univ. x 112 (MS) (1884)
- ^ Gibbs & Wilson, Vector analysis: a text-book for the use of students of mathematics and physics, founded upon the lectures of J. Willard Gibbs by Edwin Bidwell Wilson (1901)
[edit] External links
- History of Nabla
- A survey of the improper use of ∇ in vector analysis (1994) Tai, Chen
