'基因' (jīyīn) literally combines '基' (jī), meaning 'foundation' or 'base', and '因' (yīn), meaning 'cause' or 'factor'. Together, they form the scientific term 'gene'—the fundamental unit of heredity that carries genetic information from parents to offspring. Genes are segments of DNA that determine traits such as eye color, disease susceptibility, and even behavioral tendencies in humans and other living organisms.

This word is widely used in biology, medicine, and everyday discussions about health, ancestry, and biotechnology. While originally a technical term, it appears increasingly in popular media—for example, when reporting on genetic testing, CRISPR editing, or inherited conditions. It’s a formal, neutral noun; not colloquial slang, but also not overly academic for educated general use. It functions like any countable noun: you can say 一个基因 (yī gè jīyīn, 'a gene'), 多个基因 (duō gè jīyīn, 'multiple genes'), or 基因突变 (jīyīn tūbiàn, 'gene mutation').