NCI Dictionary of Cancer Terms
The NCI Dictionary of Cancer Terms features 8,300 terms related to cancer and medicine.
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- listen (a-SIH-dih-tee)
- Describes the amount of acid in a substance. An acid is a chemical that gives off hydrogen ions in water and forms salts by combining with certain metals. Acidity is measured on a scale called the pH scale. On this scale, a pH value of 7 is neutral, and a pH value of less than 7 to 0 shows increasing acidity.