What is the mathematical symbol for density?

Rho

In lower classes viz sixth standard, the first letter of the word "density" ie 'd' is used.But later in higher studies instead 'd', 'rho' the greek letter is used as the symbol for density.

rho (the Greek letter ρ) or d See the Web Links to the left for a picture. The official symbol of density, after ISO recommendations, is the Greek letter ρ (pronounced rho and writed with italic...

gottfried wihelm leibniz

The boolean negation operator is formally denoted by the not sign: ¬p. There are also other valid notations, however, including ~p or !p.