(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.object)
source: wordnet30
any histologically identifiable mass of neural cell bodies in the brain or spinal cord(noun.body)
source: wordnet30
the central structure of the lens that is surrounded by the cortex(noun.body)
A kernel; hence, a central mass or point about which matter is gathered, or to which accretion is made; the central or material portion; -- used both literally and figuratively.(noun)