Difference and relationship between protein and polypeptide

Polypeptide:
Polypeptides are usually dehydrated and condensed from 10 to 100 amino acids. Their molecular weight is less than 10,000 Dalton. They can pass through semipermeable membranes and are not precipitated by trichloroacetic acid and ammonium sulfate. In other literatures, the peptide consisting of 2 to 10 amino acids is called oligopeptide (small molecule peptide); the peptide consisting of 10 to 50 amino acids is called polypeptide; and the peptide consisting of more than 50 amino acids is called protein.
Protein:
A class of biological macromolecule widely exists in organisms. It is a kind of active macromolecule with specific stereo structure, which is formed by a peptide chain between alpha amino acids encoded by nucleic acids and formed by a peptide bond between alpha amino acids and alpha carboxyl groups. It is a macromolecule compound that a-amino acid binds in a certain order to form a polypeptide chain and then combines one or more polypeptide chains in a specific way.
The connection is that 20 basic amino acids are linked by peptide bonds.