Difference between valency , covalency ,and oxidation state

oxidation state is the charge carried by the atom if all the bonded electrons are transfered to more electronegative element.

Covalency is the number ofelectrons shared by an atom with the other atoms to form covalent bonds, e.g., Carbon can share 4 electrons, so it has 4 covalency

The valency of an element is the number of hydrogen atoms that can combine with or replace (either directly or indirectly) one atom of the element. In other words, the valency of an element is the number of electrons an atom of the element uses to combine with atoms of other elements