Sixty-four codons encode about twenty amino acids, which requires the code to be:

1. Count the codons against the amino acids they must specify. 2. There are about 20 amino acids and 64 triplet codons. 3. Three of the 64 codons terminate protein synthesis rather than adding an amino acid. 4. That still leaves far more coding codons than amino acids. 5. So a given amino acid could be encoded by more than one nucleotide triplet, making the code degenerate. _Source: OpenStax Biology 2e (CC BY 4.0), Ch 15 'Genes and Proteins', sections 15.1-15.5_