The character ∂ (Unicode: U+2202) is a stylized cursive d mainly used as a mathematical symbol, usually to denote a partial derivative such as
{\partialz}/{\partialx}
The symbol was originally introduced in 1770 by Nicolas de Condorcet, who used it for a partial differential, and adopted for the partial derivative by Adrien-Marie Legendre in 1786.[3] It represents a specialized cursive type of the letter d, just as the integral sign originates as a specialized type of a long s (first used in print by Leibniz in 1686).Use of the symbol was discontinued by Legendre, but it was taken up again by Carl Gustav Jacob Jacobi in 1841,[4] whose usage became widely adopted.[5]
The symbol is variously referred to as"partial", "curly d", "funky d", "rounded d", "curved d", "dabba", "number 6 mirrored",[6] or "Jacobi's delta",[5] or as "del" (but this name is also used for the "nabla" symbol ∇).It may also be pronounced simply "dee", "partial dee",[7] "doh",[8] or "die".[9]
The Unicode character is accessed by HTML entities ∂ or ∂, and the equivalent LaTeX symbol (Computer Modern glyph:
\partial
\partial.∂ is also used to denote the following:
| \partial(x,y,z) | |
| \partial(u,v,w) |
Dans toute la suite de ce Memoire, dz & ∂z désigneront ou deux differences partielles de z, dont une par rapport a x, l'autre par rapport a y, ou bien dz sera une différentielle totale, & ∂z une difference partielle.However, the "curly d" was first used in the form ∂u/∂x by Adrien Marie Legendre in 1786 in his 'Memoire sur la manière de distinguer les maxima des minima dans le Calcul des Variations,' Histoire de l'Académie Royale des Sciences, Annee M. DCCLXXXVI (1786), pp. 7-37, Paris, M. DCCXXXVIII (1788). On footnote of page 8, it reads:
Pour éviter toute ambiguité, je représenterai par ∂u/∂x le coefficient de x dans la différence de u, & par du/dx la différence complète de u divisée par dx.Legendre abandoned the symbol and it was re-introduced by Carl Gustav Jacob Jacobi in 1841. Jacobi used it extensively in his remarkable paper 'De determinantibus Functionalibus" Crelle's Journal, Band 22, pp. 319-352, 1841 (pp. 393-438 of vol. 1 of the Collected Works).
Sed quia uncorum accumulatio et legenti et scribenti molestior fieri solet, praetuli characteristica d differentialia vulgaria, differentialia autem partialia characteristica ∂ denotare. The "curly d" symbol is sometimes called the "rounded d" or "curved d" or Jacobi's delta. It corresponds to the cursive "dey" (equivalent to our d) in the Cyrillic alphabet." Web site: Earliest Uses of Symbols of Calculus. Aldrich, John. 16 January 2014.