The bond integrals are for example the , and for sigma, pi and delta bonds.

In the terminology of molecular orbital theory, the bonding is described as σπδ with one sigma bond, two pi bonds and one delta bond.

This means the of the five bonds present between the metal centers one is a sigma bond, two are pi bonds, and two are delta bonds.

Some ruthenium and molybdenum compounds contain a quadruple bond, consisting of one sigma bond, two pi bonds and one delta bond.

Quadruple bonds are extremely rare and can be formed only between transition metal atoms, and consist of one sigma bond, two pi bonds and one delta bond.

In chemistry, delta bonds (δ bonds) are covalent chemical bonds, where four lobes of one involved atomic orbital overlap four lobes of the other involved atomic orbital.

Sigma bonds have no nodes along the bond axis; pi bonds have a nodal plane that includes the bond axis, and delta bonds have two nodal planes, whose intersection is the bond axis.

The Greek letter δ in their name refers to d orbitals, since the orbital symmetry of the delta bond is the same as that of the usual (4-lobed) type of d orbital when seen down the bond axis.