core

1 :  a central and often foundational part usually distinct from the enveloping part by a difference in nature the core of the city: such asa :  the usually inedible central part of some fruits (such as a pineapple); especially :  the papery or leathery carpels composing the ripened ovary in a pome fruit (such as an apple)b :  the portion of a foundry mold that shapes the interior of a hollow castingc :  a vertical space (as for elevator shafts, stairways, or plumbing apparatus) in a multistory buildingd (1) :  a mass of iron serving to concentrate and intensify the magnetic field resulting from a current in a surrounding coil (2) :  a tiny doughnut-shaped piece of magnetic material (such as ferrite) used in computer memories (3) :  a computer memory consisting of an array of cores strung on fine wires; broadly :  the internal memory of a computere :  the central part of a celestial body (such as the earth or sun) usually having different physical properties from the surrounding partsf :  a nodule of stone (such as flint or obsidian) from which flakes have been struck for making implementsg :  the conducting wire with its insulation in an electric cableh :  an arrangement of a course of studies that combines under basic topics material from subjects conventionally separated and aims to provide a common background for all students core curriculumi :  the place in a nuclear reactor where fission (see ¹fission 3) occurs

2a :  a basic, essential, or enduring part (as of an individual, a class, or an entity) the staff had a core of experts the core of her beliefsb :  the essential meaning :  gist the core of the argumentc :  the inmost or most intimate part honest to the core

3 :  a part (such as a thin cylinder of material) removed from the interior of a mass especially to determine composition