| oyster |
a small animal with a soft body and a hard shell in two pieces. Oysters have a rough shell with a very shiny inside, where pearls sometimes grow. Oysters live in shallow ocean water. They are mollusks and are closely related to clams and mussels. People eat some kinds of oysters. |
| oz. |
abbreviation of "ounce" or "ounces." |
| ozone |
a form of oxygen that occurs when oxygen is exposed to an electrical charge, like lightning. It is found naturally in Earth's atmosphere. |
| 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 large amount of ozone, which absorbs certain types of harmful radiation from space. |
| P2 |
symbol of the chemical element phosphorus. |
| p |
the sixteenth letter of the English alphabet. [2 definitions] |
| p. |
abbreviation of "page." |
| PA1 |
abbreviation of "Pennsylvania." |
| pace1 |
the length of one step; stride. [8 definitions] |
| pacemaker |
a small electronic device put under the skin to control the heart rate in people with heart problems. |
| Pacific |
the largest ocean in the world. It lies between North America and Asia in the north, and South America and Australia in the south; Pacific Ocean. |
| Pacific Ocean |
the largest ocean in the world, separating Asia and North America, and Australia and South America, and extending as far south as the Southern Ocean; Pacific. |
| pacify |
to calm or bring back peace of mind to. |
| -pack |
a suffix that means a package containing that number of items. |
| pack1 |
a group of things arranged together in a container; package. [9 definitions] |
| package |
an object or bundle that is packed, wrapped, or boxed; bundle. [3 definitions] |
| packet |
a small bundle or parcel. |
| pact |
an agreement or a sworn promise. [2 definitions] |
| pad1 |
a piece of soft material used as cushioning for protection or comfort. [7 definitions] |
| paddle |
an oar with a wide, flat blade and long handle. A paddle is used with both arms for moving a small boat through the water. A paddle is not attached to the boat. [4 definitions] |