delta2
/ˈdɛltə/
noun: delta; plural noun: deltas
a triangular tract of sediment deposited at the mouth of a river, typically where it diverges into several outlets.

"the Nile delta"

noun: delta; plural noun: deltas
1.
the fourth letter of the Greek alphabet ( Δ, δ ), transliterated as ‘d’.

BRITISH
a fourth-class mark given for an essay, examination paper, or other piece of work.
the fourth in a series of items, categories, etc.
modifier noun: delta

"delta hepatitis"

ASTRONOMY
the fourth (usually fourth-brightest) star in a constellation.
noun: Delta

"Delta Cephei"

2.
a code word representing the letter D, used in radio communication.

3.
a difference between two things or values.

"there's a delta between perception and reality"

COMPUTING
a change or set of changes made to a file or program, especially as part of an update to a later version.

"this approach saves disk space by storing only data deltas"

symbol: δ; symbol: Δ; symbol: delta
1.
MATHEMATICS
variation of a variable or function.
2.
MATHEMATICS
a finite increment.
3.
MATHEMATICS
the discriminant of a quadratic equation.
4.
ASTRONOMY
declination.

The bond dipole is modeled as δ+ — δ– with a distance d between the partial charges δ+ and δ–. It is a vector, parallel to the bond axis, pointing from minus to plus, as is conventional for electric dipole moment vectors. Chemists often draw the vector pointing from plus to minus.