Write the name of linkage joining two amino acids.

Hint: An amino acid is a bi-functional organic molecule that contains both a carboxyl group, $ - {\text{COOH}}$ as well as an amine group, $ - {\text{N}}{{\text{H}}_2}$. Amino acids derived from proteins have the amino group on the alpha carbon, i.e. the carbon next to the carboxyl group.

Complete step by step answer:
Amino acids are the molecules having one amino group, one carboxyl group, one hydrogen atom and specific group ${\text{R}}$ group attached to the central carbon atom. The key elements of amino acids are ${\text{C}},{\text{N}},{\text{O}},{\text{H}}$. Amino acids are basic structural building blocks of protein.
Amino acids are classified on the basis of structure of side chain, polarity of side chain, nutritional requirements and metabolic fate. Nutritional classification of amino acids are essential and non-essential amino acids.
When two amino acids are reacted, it forms peptide bonds by removal of water molecules. Amino acids are linked together through peptide bonds forming peptides and proteins. The chains containing less than fifty amino acids are called peptides while those containing greater than fifty amino acids are called proteins.

Additional information:
$\alpha - $carboxyl group of one amino acid forms a covalent peptide bond with $\alpha - $ amino group of another amino acid by removal of a molecule of water. When two amino acids are linked by peptide bond, it is called dipeptide bond.

Note:
Dipeptide can then form a second peptide bond with a third amino acid to give tripeptide. Repetition of this process generates a polypeptide or protein of specific amino acid sequence. Each polypeptide chain starts on the left side by a free amino group of the first amino acid entering in chain formation.