div

Also an HTML tag, often found sprinkled liberally and pointlessly in HTML email sent from Hotmail accounts:

This tag extends the alignment attributes of the <p> to groups of block like elements (paragraphs, tables and images). All the block like elements within a <div> container inherit their alignment attributes from the initial <div> tag unless, of course, the elements have their own alignment attributes.

In Persian mythology, a div is a malevolent spirit or demon, created and ruled over by Ahriman. The word derives from the Sanskrit root div, meaning 'to shine'; the same root gives us the devas of Indian mythology, and - if http://www.geocities.com/rastamage/BoS/Nigromancy/daimonsriddle.html is to be believed - the word devil (Chambers seems to contradict this, saying that its root diabolos originally meant 'to throw across').

Div is also an abbreviation for dividend, and in Scottish English it is a form of do (as a present indicative). Finally, it is the name of an irascible, alcoholic DivX player in the webcomic Penny Arcade.

Short for the divergence of a quantity. In an orthogonal coordinate system with coordinates {u₁,u₂,u₃}, where a line element ds is given by

ds²=h₁² du₁² + h₂² du₂² + h₃² du₃²

div A = (1/h₁ h₂ h₃)(δ/δu₁ {h₂ h₃ A₁} i₁ + δ/δu₂ {h₃ h₁ A₂} i₂ + δ/δu₃ {h₁ h₂ A₃} i₃)

In cylindrical coordinates

{u₁,u₂,u₃} = {R,φ,Z}
{h₁,h₂,h₃} = {1,R,1}

'Div' is usually represented by a triangle 'pointing' downwards followed by a full stop (to distinguish it from grad)

'div' is often used in electromagnetic theory. Together with its cousin the operator 'curl' it allows an elegant expresion of Maxwell's equations. For example the the empirical obervation that there are no magnetic monopoles is expressed in one of those venerable equations as

div.B = 0

See also grad.