Synonymous substitution is a technical term used in genetics and molecular biology to describe a genetic change where the DNA sequence is altered, but the corresponding protein sequence remains unchanged. This phenomenon is observed when the change in the genetic code results in a codon that codes for the same amino acid as the original codon. Synonymous substitution can also be referred to as silent mutation, silent substitution, or synonymous mutation. These different terms all describe the same concept of a mutation that does not alter the amino acid sequence of a protein. Synonymous substitution can have implications in the evolution of genes and understanding genetic diseases.