Answer:
When a single amino acid is encoded by more than one codon.
Explanation:
Degeneracy is when a single amino acid is encoded by more than one codon. This pehonomenon was first described by Lagerkvist where there are more codons than amino acids that could be encoded.
There are 6 elements that are the most important. The acronym, CHNOPS, is an easy way to remember these.
C - Carbon
H - Hydrogen
N - Nitrogen
O - Oxygen
P - Phosphorous
S - Sulfur
"A" bonds with "T", and "G" bonds with "C" (A-T) (G-C)