Glossary
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| Term | Definition |
|---|---|
| Ocean heat content | The total amount of heat stored in the ocean. The oceans have absorbed about 90 percent of the extra heat trapped by greenhouse gases since the 1970s. Climate Change |
| Ocean warming | The rise in ocean temperatures caused by the oceans absorbing excess heat. It contributes to sea-level rise, coral bleaching, stronger storms, and shifts in marine life. Climate Change |
| Open Science | Practices that make research methods, data, code and publications freely accessible so others can scrutinize and reproduce them. Science General |
| Open-weight model | An AI model whose trained weights are publicly released, allowing anyone to run or modify it. It is not always fully open-source, since training data and code may be withheld. Artificial Intelligence |
| Oral polio vaccine | A live attenuated polio vaccine given by mouth. It is cheap and stops transmission well, but in rare cases the weakened virus can mutate and cause vaccine-derived polio, so many countries now use the injected inactivated vaccine. Vaccines |
| Orbit | The curved path of an object around a star, planet, or moon, due to gravity. Science General |
| Order of magnitude | A factor of ten. Two quantities that differ by one order of magnitude differ by about ten times. Science General |
| Organic chemistry | The branch of chemistry that studies carbon-based compounds, including those found in living things. Science General |
| Outbreak | A sudden rise in cases of a disease in a particular place or group. Outbreaks of vaccine-preventable diseases often occur in communities with low vaccination rates. Vaccines |
| Outlier | A data point in a set of data that is much bigger or much smaller than the rest of the set. Science General |