1. The center of an object.
2. The central part of the earth.
3. The region of a nuclear reactor containing the fissile material where the reaction takes place.
4. A small group of indispensable persons or things; SYN. nucleus, core group.
5. A rod of magnetic material (as soft iron) that passes through a coil and serves to increase the inductance of the coil.
6. A cylindrical sample of soil or rock obtained with a hollow drill.
In earth science, the innermost part of Earth. It is divided into an outer core, which begins at a depth of 2,898 km/1,800 mi, and an inner core, which begins at a depth of 4,982 km/3,095 mi. Both parts are thought to consist of iron-nickel alloy. The outer core is liquid and the inner core is solid.
Evidence for the nature of the core comes from seismology (observation of the paths of earthquake waves through Earth), and calculations of Earth's density. The temperature of the core is estimated to be at least 4,000şC/7,232şF.
In archeology, a solid cylinder of sediment or soil collected with a coring device and used to evaluate the geological context and stratigraphy of archeological material or to obtain paleobotanical samples. Core can also mean the tool used to extract a core sample from the ground, or a stone blank from which flakes or blades are removed.
One of the types of memory built into computers before random access memory (RAM) was available or affordable. Some people still use the term to refer to the main memory of any computer system, as in the phrase core dump—a listing of the raw contents of main memory at the moment of a system crash. Compare RAM.