### Question
How is the term bioavailability defined?


### Answer
The term **bioavailability** is defined in *21 U.S.C. § 355* as the following:

> the rate and extent to which the active ingredient or therapeutic ingredient is absorbed from a drug and becomes available at the site of drug action

#### Citation:
  - *21 U.S.C. § 355*
  - Heading: **CHAPTER 9-FEDERAL FOOD, DRUG, AND COSMETIC ACT > SUBCHAPTER V-DRUGS AND DEVICES > Part A-Drugs and Devices**

