a part of the cell containing DNA and RNA and responsible for growth and reproduction
any histologically identifiable mass of neural cell bodies in the brain or spinal cord
the positively charged dense center of an atom
(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
a single undivided whole; "an idea is not a unit that can be moved from one brain to another"
an organization regarded as part of a larger social group; "the coach said the offensive unit did a good job"; "after the battle the soldier had trouble rejoining his unit"
a single undivided natural thing occurring in the composition of something else; "units of nucleic acids"
an individual or group or structure or other entity regarded as a structural or functional constituent of a whole; "the reduced the number of units and installations"; "the word is a basic linguistic unit"
notion consisting of a narrow strip of fine material used for trimming
a long strip of inked material for making characters on paper with a typewriter
any long object resembling a thin line; "a mere ribbon of land"; "the lighted ribbon of traffic"; "from the air the road was a grey thread"; "a thread of smoke climbed upward"
the branch of quantum physics that accounts for matter at the atomic level; an extension of statistical mechanics based on quantum theory (especially the Pauli exclusion principle)
impossible or difficult to perceive by the mind or senses; "an imperceptible drop in temperature"; "an imperceptible nod"; "color is unperceivable to the touch"