• noun:   a part of the cell containing DNA and RNA and responsible for growth and reproduction
• noun:   any histologically identifiable mass of neural cell bodies in the brain or spinal cord
• noun:   the positively charged dense center of an atom
• noun:   (astronomy) the center of the head of a comet; consists of small solid particles of ice and frozen gas that vaporizes on approaching the sun to form the coma and tail
• noun:   a small group of indispensable persons or things

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