what is mby degeneracy of d orbital
I guess you are asking "what is mean by degeneracy of d orbital"
Those orbitals which contain equal energy are called degenerated orbitals.In the absence of an external magnetic field, all the five d-orbitals are degenerate that is of equal energy. As the magnetic field is applied they split into two sets of orbital known as t2g and eg. The t2g set of orbitals consists of three degenerate (that is having same energy) orbitals while the eg set consists of two degenerate orbitals. So the t2g is triply degenerate while eg is doubly degenerate.
Those orbitals which contain equal energy are called degenerated orbitals.In the absence of an external magnetic field, all the five d-orbitals are degenerate that is of equal energy. As the magnetic field is applied they split into two sets of orbital known as t2g and eg. The t2g set of orbitals consists of three degenerate (that is having same energy) orbitals while the eg set consists of two degenerate orbitals. So the t2g is triply degenerate while eg is doubly degenerate.