*f'(x)* for the first derivative, *f''(x)* for the second derivative, etc., were introduced by
Joseph Louis Lagrange (1736-1813). In 1797 in
*Théorie des fonctions analytiques*
the symbols *f'x* and *f''x* are found; in the
*Oeuvres, Vol. X*,
"which purports to be a reprint of the 1806 edition, on p. 15, 17, one finds the corresponding parts
given as *f(x), f'(x), f''(x), f'''(x)*" (Cajori vol. 2, page 207).

In 1770 Joseph Louis Lagrange (1736-1813) wrote for in his memoir
*Nouvelle méthode pour résoudre les équations littérales par le moyen des séries*
(Oeuvres, Vol. III, pp. 5-76).
The notation also occurs in a memoir by François Daviet de Foncenex in 1759
believed actually to have been written by Lagrange (Cajori 1919, page 256).

In 1772 Lagrange wrote *u'* = *du*/*dx* and
*du* = *u'dx* in "Sur une nouvelle espèce de calcul relatif à
la différentiation et à l'integration des quantités variables,"
*Nouveaux Memoires de l'Academie royale des Sciences et Belles-Lettres de Berlin*
(Oeuvres, Vol. III, pp. 451-478).

*D _{x} y* was introduced by
Louis François Antoine Arbogast
(1759-1803) in "De Calcul des dérivations et ses usages dans la théorie des suites
et dans le calcul différentiel," Strasbourg, xxii, pp. 404, Impr. de Levrault,
fréres, an VIII (1800). (This information comes from Julio González Cabillón;
Cajori indicates in his

*D* was used by Arbogast in the same work, although this symbol
had previously been used by Johann Bernoulli (Cajori vol. 2, page
209). Bernoulli used the symbol in a non-operational sense (Maor,
page 97).

**Partial derivative.** The "curly d" was used in 1770 by
Antoine-Nicolas Caritat, Marquis de Condorcet
(1743-1794) in "Memoire sur les Equations aux différence partielles,"
which was published in
*Histoire de L'Academie Royale des Sciences,*
pp. 151-178, Annee M. DCCLXXIII (1773).
On page 152, Condorcet says:

Dans toute la suite de ce Memoire,However, the "curly d" was first used in the form by Adrien Marie Legendre in 1786 in his "Memoire sur la manière de distinguer les maxima des minima dans le Calcul des Variations,"dz&zdésigneront ou deux differences partielles dez,, dont une par rapport ax,l'autre par rapport ay,ou biendzsera une différentielle totale, &zune difference partielle. [Throughout this paper, bothdz&zwill either denote two partial differences ofz,where one of them is with respect tox,and the other, with respect toy,ordzandzwill be employed as symbols of total differential, and of partial difference, respectively.]

Pour éviter toute ambiguité, je répresentarie par le coefficient deLegendre 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 thexdans la différence deu,& par la différence complète deudivisée pardx.

Sed quia uncorum accumulatio et legenti et scribenti molestior fieri solet, praetuli characteristicaThe "curly d" symbol is sometimes called the "rounded d" or "curved d" or

ddifferentialia vulgaria, differentialia autem partialia characteristica

denotare.

**Integral.** Before introducing the integral symbol, Leibniz
wrote omn. for "omnia" in front of the term to be integrated.

The integral symbol was first used by Gottfried Wilhelm Leibniz
(1646-1716) on October 29, 1675, in an unpublished manuscript.
Several weeks later, on Nov. 21, he first placed *dx* after the
integral symbol (Burton, page 359). Later in 1675, he proposed the
use of the symbol in a letter to Henry Oldenburg, secretary of the
Royal Society: "Utile erit scribi pro omnia, ut *l* = omn.
*l*, id est summa ipsorum *l*" [It will be useful to write
for omn. so
that *l* = omn. *l*, or the sum of all the
*l*'s.] The first appearance of the integral symbol in print
was in a paper by Leibniz in the *Acta Eruditorum.* The integral
symbol was actually a long letter S for "summa."

In his *Quadratura curvarum* of 1704, Newton wrote a small
vertical bar above x to indicate the integral of x. He wrote two
side-by-side vertical bars over x to indicate the integral of (x with
a single bar over it). Another notation he used was to enclose the
term in a rectangle to indicate its integral. Cajori writes that
Newton's symbolism for integration was defective because the x with a
bar could be misinterpreted as x-prime and the placement of a
rectangle about the term was difficult for the printer, and that
therefore Newton's symbolism was never popular, even in England.

**Limits of integration.** Limits of integration were
first indicated only in words. Euler was the first to use a symbol
in *Institutiones calculi integralis,* where he wrote the
limits in brackets and used the Latin words *ab* and *ad*
(Cajori vol. 2, page 249).

The modern definite integral symbol was originated by Jean
Baptiste Joseph Fourier (1768-1830). In 1822 in his famous *The Analytical
Theory of Heat* he wrote:

Nous désignons en général par le signe l'intégrale qui commence lorsque la variable équivaut àThe citation above is from "Théorie analytique de la chaleur" [The Analytical Theory of Heat], Firmin Didot, Paris, 1822, page 252 (paragraph 231).a,et qui est complète lorsque la variable équivaut àb. . .

Fourier had used this notation somewhat earlier in the
*Mémoires* of the French Academy for 1819-20, in an
article of which the early part of his book of 1822 is a reprint
(Cajori vol. 2 page 250).

The **bar notation** to indicate evaluation of an antiderivative
at the two limits of integration was first used by Pierre Frederic
Sarrus (1798-1861) in 1823 in Gergonne's *Annales,* Vol. XIV.
The notation was used later by Moigno and Cauchy (Cajori vol. 2, page
250).

**Integration around a closed path.** Dan Ruttle, a reader of this page, has found a use of the integral
symbol with a circle in the middle by
Arnold Sommerfeld (1868-1951)
in 1917 in *Annalen der
Physik,* "Die Drudesche Dispersionstheorie vom Standpunkte des
Bohrschen Modelles und die Konstitution von H2, O2 und N2." This use
is earlier than the 1923 use shown by Cajori. Ruttle reports that J.
W. Gibbs used only the standard integral sign in his *Elements of
Vector Analysis* (1881-1884), and that and E. B. Wilson used a
small circle below the standard integral symbol to denote integration
around a closed curve in his *Vector Analysis* (1901, 1909) and
in *Advanced Calculus* (1911, 1912).

**Limit.** lim. (with a period) was used first by
Simon-Antoine-Jean L'Huilier (1750-1840).
In 1786, L'Huilier gained
much popularity by winning the prize offered by *l'Academie royale
des Sciences et Belles-Lettres de Berlin*. His essay, "Exposition
élémentaire des principes des calculs superieurs,"
accepted the challenge thrown by the Academy -- a clear and precise
theory on the nature of infinity. On page 31 of this remarkable paper,
L'Huilier states:

Pour abreger & pour faciliter le calcul par une notation plus commode, on est convenu de désigner autrement que parlim (without a period) was written in 1841 by Karl Weierstrass (1815-1897) in one of his papers published in 1894 in,

la limite du rapport des changements simultanes de

P& dex,favoir par;

en sorte que

ou

;

designent la même chose

The arrow notation for limits was introduced by Godfrey Harold Hardy (1877-1947) in his remarkable "A Course of Pure Mathematics," Cambridge: At the University Press, xv, pp. 428, 1908. Check the preface of this first edition (Julio González Cabillón and Cajori vol. 2, page 257).

**Infinity.** The infinity symbol was introduced by
John Wallis (1616-1703)
in 1655 in his *De sectionibus conicis* (On Conic Sections) as follows:

Suppono in limine (juxta^ Bonaventurae CavalleriiWallis also used the infinity symbol in various passages of hisGeometriam Indivisibilium) Planum quodlibet quasi ex infinitis lineis parallelis conflari: Vel potiu\s (quod ego mallem) ex infinitis Prallelogrammis [sic] aeque\ altis; quorum quidem singulorum altitudo sit totius altitudinis 1/, sive alicuota pars infinite parva; (esto enim nota numeri infiniti;) adeo/q; omnium simul altitude aequalis altitudini figurae.

Cum enim primus terminus in serie Primanorum sit 0, primus terminus in serie reciproca erit vel infinitus: (sicut, in divisione, si diviso sit 0, quotiens erit infinitus)In

Cajori (vol. 2, p 44) says the conjecture has been made that Wallis
adopted this symbol from the late Roman symbol for 1,000. He attributes the
conjecture to Wilhelm Wattenbach (1819-1897),
*Anleitung zur lateinischen Paläographie* 2. Aufl.,
Leipzig: S. Hirzel, 1872. Appendix: p. 41.

This conjecture is lent credence by the labels inscribed on a Roman
hand abacus stored at the Bibliothèque Nationale in Paris. A
plaster cast of this abacus is shown in a photo on page 305 of the
English translation of Karl Menninger's *Number Words and Number
Symbols*; at the time, the cast was held in the Cabinet des
Médailles in Paris. The photo reveals that the column devoted
to 1000 on this abacus is inscribed with a symbol quite close in
shape to the lemniscate symbol, and which Menninger shows would
easily have evolved into the symbol M, the eventual Roman symbol for
1000 [Randy K. Schwartz].

[Julio González Cabillón contributed to this entry.]

**Delta to indicate a small quantity.** In 1706,
Johann Bernoulli
used δ to denote the difference of functions. Julio González Cabillón believes this
is probably one of the first if not the first use of delta in this sense.

**Delta and epsilon.** Augustin-Louis Cauchy
(1789-1857) used ε in 1821 in *Cours d'analyse*
(Oeuvres II.3),
and sometimes used δ instead (Cajori vol. 2, page 256). According to Finney and Thomas (page
113), "δ meant 'différence' (French for *difference*
and ε meant 'erreur' (French for *error*)."

The first theorem on limits that Cauchy sets out to prove in the *Cours d'Analyse*
(Oeuvres II.3, p. 54)
has as hypothesis that

The proof then begins by saying

denote by ε a number as small as one may wish. Since the increasing values of[William C. Waterhouse]xmake the differencef(x+ 1) -f(x) converge to the limitk,one can assign a sufficiently substantial value to a numberhso that, forxbigger than or equal toh, the difference in question is always between the boundsk- ε,k+ ε.

The first delta-epsilon proof is Cauchy's proof of what is essentially the mean-value theorem for derivatives. It comes from his lectures on the Calcul infinitesimal, 1823, Leçon 7, in Oeuvres, Ser. 2, vol. 4, pp. 44-45. The proof translates Cauchy's verbal definition of the derivative as the limit (when it exists) of the quotient of the differences into the language of algebraic inequalities using both delta and epsilon. In the 1820s Cauchy did not specify on what, given an epsilon, his delta or n depended, so one can read his proofs as holding for all values of the variable. Thus he does not make the distinction between converging to a limit pointwise and convering to it uniformly.

[Judith V. Grabiner, author of *The Origins of Cauchy's Rigorous Calculus* (MIT, 1981)]

**For vector analysis entries on the Words pages,
see here for a list.**

The vector differential operator, now written
and called *nabla* or *del*, was introduced by William Rowan Hamilton
(1805-1865). Hamilton wrote the operator as
and it was P. G. Tait who established
as the conventional symbol--see his *An Elementary Treatise on Quaternions*
(1867). Tait was also responsible for establishing the term *nabla*. See
NABLA on the Earliest Uses of Words page.

David Wilkins suggests that Hamilton may have used the nabla
as a general purpose symbol or abbreviation for whatever operator he wanted
to introduce at any time. In 1837 Hamilton used the nabla, in its modern orientation,
as a symbol for any arbitrary function in *Trans. R. Irish Acad.* XVII.
236. (OED.) He used the nabla to signify a permutation operator in "On
the Argument of Abel, respecting the Impossibility of expressing a Root of any
General Equation above the Fourth Degree, by any finite Combination of Radicals
and Rational Functions," *Transactions of the Royal Irish Academy,*
18 (1839), pp. 171-259.

Hamilton used the rotated nabla, i.e.
,
for the vector differential operator in the "Proceedings of the Royal Irish Academy" for the meeting
of July 20, 1846. This paper appeared in volume 3 (1847), pp. 273-292. Hamilton
also used the rotated nabla as the vector differential operator in "On
Quaternions; or on a new System of Imaginaries in Algebra"; which he published
in instalments in the *Philosophical Magazine* between 1844 and 1850. The
relevant portion of the paper consists of articles 49-50, in the instalment
which appeared in October 1847 in volume 31 (3rd series, 1847) of the Philosophical
Magazine, pp. 278-283. A footnote in vol. 31, page 291, reads:

In that paper designed for Southampton the characteristic was written ; but this more common sign has been so often used with other meanings, that it seems desirable to abstain from appropriating it to the new signification here proposed.Wilkins writes that "that paper" refers to an unpublished paper that Hamilton had prepared for a meeting of the British Association for the Advancement of Science, but which had been forwarded by mistake to Sir John Herschel's home address, not to the meeting itself in Southampton, and which therefore was not communicated at that meeting. The footnote indicates that Hamilton had originally intended to use the nabla symbol that is used today but then decided to rotate it to avoid confusion with other uses of the symbol.

The rotated form appears in Hamilton's magnum opus, the
*
Lectures on Quaternions* (1853, p. 610).

Cajori (vol. 2, page 135) and the OED give this reference.

According to Stein and Barcellos (page 836), Hamilton denoted the gradient with an ordinary capital delta in 1846. However, this information may be incorrect, as David Wilkins writes that he has never seen the gradient denoted by an ordinary capital delta in any paper of Hamilton published in his lifetime.

David Wilkins of the School of Mathematics at Trinity College in Dublin has made available texts of the mathematical papers published by Hamilton in his lifetime at his History of Mathematics website.

grad as a symbol for gradient appears in H. Weber's *Die partiellen differential-gleichungen
der mathematischen physik nach Riemanns Vorlesungen* of 1900 (Cajori vol. 2, page 135). See
GRADIENT on the Earliest Uses of Words page.

William Kingdon Clifford (1845-1879) used *div u* or *dv u* as symbols for divergence (Cajori vol. 2, page
135).

The symbol Δ for the Laplacian operator (also represented by
^{2})
was introduced by Robert Murphy
in 1833 in *Elementary Principles of the Theories of Electricity.* (Kline, page 786).
See LAPLACE'S OPERATOR on the Earliest Uses of Words page.

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