| 释义 |
▪ I. del Math.|dɛl|
[Short for delta, from its being represented by an inverted delta (sense 1).]
A name of the symbolic operator ∇, defined as i ∂ / ∂x + j ∂ / ∂y + k ∂ / ∂z .
1901Gibbs & Wilson Vector Analysis iii. 138, i ∂ / ∂x + j ∂ / ∂y + k ∂ / ∂z . 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 formulæ in which ∇ occurs a number of times no inconvenience to the speaker or hearer arises from the repetition. ∇V is read simply as ‘del V’. 1924C. E. Weatherburn Adv. Vector Analysis i. 4 ∇V (pronounced del V). 1962Corson & Lorrain Introd. Electromagn. Fields i. 6 Gradient is commonly abbreviated as grad, and the operation on the scalar f defined by the term gradient is indicated by the symbol ∇, called del. 1964S. Simons Vector Anal. v. 69 If we define a vector differential operator ∇ (called ‘del’ or ‘nabla’) by ∇ = i(∂/∂x) + j(∂/∂y) + k(∂/∂z), then it follows..that grad V = ∇V.
▪ II. del
obs. f. deal n.1, and of dole, mourning. |