what is meant by chelation & denticity

Chelation:Chelation is the formation or presence of two or more separate bindings between a polydentate (multiple bonded) ligand and a single central atom.

Denticity: Denticity refers to the number of atoms in a single ligand that bind to a central atom in a coordination complex. In many cases, only one atom in the ligand binds to the metal, so the denticity equals one, and the ligand is said to be monodentate (sometimes called unidentate). Ligands with more than one bonded atom are called polydentate or multidentate.