(physics) A radioactive isotope of nitrogen, ¹³₇N, having seven protons and six neutrons, and a half-life of less than ten minutes; it is used in positron emission tomography

(physics) A stable isotope of nitrogen, ¹⁵₇N, having seven protons and eight neutrons; it accounts for less than 0.4% of the natural element; it is used in nuclear magnetic resonance spectroscopy

(physics) A stable isotope of nitrogen, ¹⁴₇N, having seven protons and seven neutrons; it accounts for over 99% of the natural element.

(physics, astronomy) A group of nuclear reactions, that involve the interaction of protons with carbon, nitrogen and oxygen nuclei, thought to be the main source of energy in main-sequence stars of greater than 1.4 solar mass.

A device that adsorbs nitrogen oxides produced by a lean-burn engine, such as a diesel.

plural of lean nitrogen oxide trap