What is a peptide consisting of three amino acid residues called?

A peptide that contains three amino acid residues is specifically referred to as a tripeptide. This terminology is derived from the prefix "tri-" which means three. In biochemistry, peptides are short chains of amino acids linked by peptide bonds, and their names often indicate the number of amino acids they contain. A tripeptide would thus be formed by the combination of three amino acids via peptide bonds.

In contrast, a polypeptide refers to a longer chain of amino acids, typically more than ten, while a di-peptide consists of exactly two amino acid residues. The term monopeptide is not commonly used, as it suggests a single amino acid which typically wouldn't form a peptide bond by itself. Therefore, the term tripeptide accurately describes a peptide made up of precisely three amino acids.