The a common nonmetallic element that is normally a colorless odorless tasteless inert diatomic gas; constitutes 78 percent of the atmosphere by volume; a constituent of all living tissues a nonmetallic element belonging to the halogens; used especially in medicine and photography and in dyes; occurs naturally only in combination in small quantities (as in sea water or rocks) a metric unit of weight equal to one thousandth of a kilogram a nonmetallic univalent element that is normally a colorless and odorless highly flammable diatomic gas; the simplest and lightest and most abundant element in the universe a base found in DNA (but not in RNA) and derived from pyrimidine; pairs with adenine the basic unit of length adopted under the Systeme International d’Unites (approximately 1.094 yards) a metric unit of length equal to one ten billionth of a meter (or 0.0001 micron); used to specify wavelengths of electromagnetic radiation a unit of radiation exposure; the dose of ionizing radiation that will produce 1 electrostatic unit of electricity in 1 cc of dry air a fat-soluble vitamin that is essential for normal reproduction; an important antioxidant that neutralizes free radicals in the body 1/60 of a minute; the basic unit of time adopted under the Systeme International d’Unites