Bioavailability is a measure of how much of a substance, such as a drug or nutrient, is absorbed and made available in the body for use or distribution to tissues and organs. It is an important factor in determining the effectiveness of a substance in producing its desired effect. Bioavailability can be influenced by various factors, including the route of administration, the formulation of the substance, and individual differences in metabolism. Researchers in this area aim to understand and improve the bioavailability of substances to optimize their therapeutic or nutritional benefits.