Glossary
Partial-word, boolean (AND, OR, NOT) and "exact phrase" searches are supported.
| Term | Definition |
|---|---|
| Herd immunity | Indirect protection for people who are not immune that occurs when enough of the population is immune that a disease cannot spread easily. Also called community immunity. Vaccines |
| Herd immunity threshold | The proportion of a population that must be immune to stop sustained spread of a disease. It is about 95 percent for measles because measles is extremely contagious. Vaccines |
| Heredity | The passing of traits from parents to offspring through genes. Science General |
| Heritability | The proportion of variation in a trait within a population that is due to genetic differences. It does not describe how much of an individual's trait is genetic. Genetics |
| Heuristics | A heuristic is a mental shortcut or "rule of thumb" that helps people make quick, practical decisions and solve complex problems without spending a lot of time or mental energy. Science General |
| Hierarchy of Evidence | A ranking of study types by how strongly they support causal conclusions, typically from anecdotes and case reports at the bottom to randomized trials and systematic reviews at the top. Science General |
| Hired gun | An expert paid to provide testimony or commentary that supports a client's position, regardless of the broader evidence. Science Literacy |
| HIV | HIV (Human Immunodeficiency Virus) is a virus that attacks the body's immune system, specifically targeting CD4 T cells, and can lead to AIDS (Acquired Immunodeficiency Syndrome) if left untreated. Public Health |
| Hockey Stick Graph | A reconstruction of Northern Hemisphere temperatures over the past millennium showing a sharp rise in the 20th century. Repeatedly attacked by deniers and repeatedly confirmed. Climate Change |
| Holocene | The geological epoch that began about 11,700 years ago after the last ice age, during which a relatively stable climate allowed agriculture and civilization to develop. Climate Change |