noun
: a heavy isotope of carbon having the mass number 13, constituting about 1/70 of natural carbon, and used in tracer studies in chemistry and biology — symbol C 13 or 13 C
noun
: a heavy isotope of carbon having the mass number 13, constituting about 1/70 of natural carbon, and used in tracer studies in chemistry and biology — symbol C 13 or 13 C
Webster's New International English Dictionary. Новый международный словарь английского языка Webster. 2012