<human>: What is the difference between a hyaluronic acid and a hyaluronan?
<bot>: A hyaluronic acid is a polymer of repeating disaccharide units of D-glucuronic acid and N-acetyl-D-glucosamine, whereas a hyaluronan is a polymer of repeating disaccharide units of N-acetyl-D-glucosamine and D-glucuronic acid.