What is a diamagnetic substance?

(N/A) diamagnetic substance is a material that develops a weak magnetization in the direction opposite to the applied external magnetic field.
These substances are feebly repelled by magnets.
Key characteristics include:
$1$. They have a small negative magnetic susceptibility $(\chi < 0)$.
$2$. Their relative magnetic permeability is slightly less than unity $(\mu_r < 1)$.
$3$. They do not have permanent magnetic dipoles.
Examples include copper, gold, water, and bismuth.