What is the difference between van der Waals radius and covalent radius?

(N/A) The van der Waals radius is defined as half of the distance between the nuclei of two non-bonded adjacent atoms of the same element in a solid state.
The covalent radius is defined as half of the distance between the nuclei of two atoms bonded by a single covalent bond in a molecule.
Generally,the van der Waals radius is greater than the covalent radius $(r_{vdW} > r_{cov})$.