| oxide |
a compound that includes oxygen. |
| oxidize |
to combine with oxygen, as in burning or rusting. [4 definitions] |
| oxygen |
a chemical element that has eight protons in each nucleus and that occurs in pure form, as a colorless, odorless gas essential to the respiration of living things, or in important compounds such as water, carbohydrates, and oxide minerals. (symbol: O) |
| oyster |
any of various edible mollusks found chiefly in shallow water and characterized by a lumpy, irregular bi-valved shell, esp. the pearl oyster. [3 definitions] |
| oz. |
abbreviation of "ounce," or "ounces," a unit of weight equal to one sixteenth of a pound or 28.350 grams in the avoirdupois weight system, and equal to one twelfth of a pound or 31.1051 grams in the apothecaries' weight and the troy weight systems. |
| ozone |
oxygen in the form of molecules with three atoms, created by exposure of oxygen to electrical discharge or ultraviolet radiation, having a sharp smell, and being an effective oxidant for use in bleaching and sterilizing. |
| ozone hole |
an area in the ozone layer where the ozone becomes thin. There is a large ozone hole over Antarctica and a smaller one over the North Pole. Scientists warn us this is dangerous. |
| ozone layer |
an atmospheric layer between ten and twenty miles above the earth that contains a substantial concentration of ozone, which absorbs ultraviolet radiation from space and prevents some heat loss from the earth; ozonosphere. |
| P2 |
symbol of the chemical element phosphorus. |
| p |
the sixteenth letter of the English alphabet. [3 definitions] |
| p. |
abbreviation of "page," one side of a sheet of printed or written paper. [2 definitions] |
| PA1 |
abbreviation of "Pennsylvania," an eastern U.S. state south of New York. |
| pace1 |
the length of one stride in walking. [12 definitions] |
| pacemaker |
a small electronic device implanted under the skin to regulate the heart rate in patients with heart problems. [3 definitions] |
| Pacific |
of or pertaining to the Pacific Ocean. [2 definitions] |
| Pacific Ocean |
the largest ocean in the world, separating Asia and North America, and Australia and South America, and extending to Antarctic; Pacific. |
| pacify |
to calm or restore peace of mind to. [2 definitions] |
| -pack |
a package containing (so many) items, usu. cans or bottles. |
| pack1 |
a container for goods or belongings, usu. flexible and carried on the back. [16 definitions] |
| package |
an object or bundle that is packed, wrapped, or boxed; parcel. [6 definitions] |
| packet |
a small bundle or parcel. [2 definitions] |