Conflicting definitions of what makes up a protein? PLEASE help, exams soon!

First my book says:

"a protein is a functional unit made up of one or more polypeptide chains"

Then it says:

"Proteins are chains of over 100 amino acids."

Those are really different definitions! What if the chain is 110 amino acids long? By the first definition it's not a protein, because it's not long enough to be two polypeptide chains. But by the second definition it is a protein, because it's more than 100 amino acids long.

Please help, and thank you very much!

Ok, a protein is made up of many amino acids held together by peptide bonds. Polypeptides literally are like a string of over hundreds of amino acids covalently bonded.

So in reality, definitions both are correct. If it is 110 amino acids long, it is still a protein by the first one because, its still a polypeptide. What you need to realise is that the polypeptide would fold in secondary and tertiary structures forming more chan one chain.

Amino acids >> peptide chain(s) >> protein

Amino acids make up a polypeptide chain. Protein is made up of a single or multiple combinations of polypeptide chains. It's the same basic structure but different levels of structural complexity.