Glossary
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| Term | Definition |
|---|---|
| Hasty generalization | Drawing a broad conclusion from too few or unrepresentative examples. Science Literacy |
| Heat | The transfer of thermal energy from a warmer object to a cooler one. Science General |
| Heat dome | A persistent area of high atmospheric pressure that traps hot air over a region, producing prolonged and intense heat waves. Climate Change |
| Heat index | A measure of how hot it feels to the human body when humidity is combined with air temperature. High humidity reduces the body's ability to cool by sweating. Climate Change |
| Heat wave | A period of unusually hot weather lasting several days or more. Heat waves have become more frequent and intense as the climate warms. Climate Change |
| Helper T cell | A type of T cell, also called a CD4 T cell, that coordinates the immune response by helping B cells make antibodies and activating other immune cells. Vaccines |
| Hepatitis A vaccine | An inactivated vaccine that protects against hepatitis A, a liver infection spread mainly through contaminated food and water. Vaccines |
| Hepatitis B birth dose | A dose of hepatitis B vaccine given within 24 hours of birth to protect newborns from infection passed from their mothers, which can lead to lifelong liver disease and cancer. Vaccines |
| Hepatitis B vaccine | A recombinant vaccine that protects against hepatitis B virus, a major cause of liver cirrhosis and liver cancer. It was the first vaccine to prevent a type of cancer. Vaccines |
| Herd (Community) Immunity | A situation in which a sufficient proportion of a population is immune to an infectious disease (through vaccination and/or prior illness) to make its spread from person to person unlikely. Even individuals not vaccinated (such as newborns and those with chronic illnesses) are offered some protection because the disease has little opportunity to spread within the community. Vaccines |