What is "coordination bond" (chemistry)?

Coordination bond is a special valence bond, which is characterized by that a pair of electrons used by * * * come from the same atom. The condition for forming a coordination bond is that one atom has a lone electron pair and the other atom has an empty orbit. There are many kinds of coordination compounds, especially transition metal complexes, which are widely used and have formed coordination chemistry.

Everything you know now contains coordination bonds: ammonium sulfate, carbon monoxide and all the complexes you know (all complexes are bound by coordination bonds) ...

There are a pair of electron pairs (lone electron pairs) in the nitrogen atom of ammonia molecule that do not participate in bonding.

Hydrogen ions in solution have an empty orbit without electrons. When an ammonia molecule absorbs a proton, a pair of lone electrons of the nitrogen atom fills the empty 1s orbit of the hydrogen ion, forming a coordination valence bond.

The difference between coordination bonds and general valence bonds is that the bonding electron pairs are not provided by two bonding atoms, but from one of them (the central atom).

And water and hydrogen ions H3O+