核糖核酸(RNA)
全名ribonucleic acid
两种主要的核酸之一（另一种是DNA），负责在所有活细胞细胞蛋白质的合成作用，并在有些病毒取代DNA作为遗传资讯的媒介。就像DNA一样，RNA是由核酸股一节一节结合而成，只是股是单独而非像DNA是成双的，且在DNA胸腺嘧啶的地方由尿嘧啶取代。传讯RNA（mRNA）是从DNA股复制而来的单独股，当作其样板，携带来自DNA的遗传码讯息（在染色体之中）到蛋白质合成的地方（核醣体）。核醣体RNA（rRNA）是核醣体建构材料的一部分，参与蛋白质合成。转移RNA（tRNA）是最小的一种，核酸单位少於100（mRNA与rRNA的单位数以千计）。MRNA上的每个核酸三联体具体说明氨基酸将要合成的蛋白质，而tRNA分子在突出端具有三联体的互补体，指定氨基酸到链结成蛋白质的定位。还存在各种较小的RNA种类，至少有些是作为催化剂（核醣），长久以来认为专属蛋白质的功能。
English version：
RNA
One of the two main types of nucleic acid (the other being DNA), which functions in cellular protein synthesis in all living cells and replaces DNA as the carrier of genetic information in some viruses. Like DNA, it consists of strands of nucleotides joined along their length, but the strands are single and it has uracil (U) where DNA has thymine. Messenger RNA (mRNA), a single strand copied from a DNA strand that acts as its template, carries the message of the genetic code from DNA (in chromosomes) to the site of protein synthesis (on ribosomes). Ribosomal RNA (rRNA), part of the building material of ribosomes, participates in protein synthesis. Transfer RNA (tRNA), the smallest type, has fewer than 100 nucleotide units (mRNA and rRNA contain thousands). Each nucleotide triplet on mRNA specifies which amino acid comes next on the protein being synthesized, and a tRNA molecule with that triplet's complement on its protruding end brings the specified amino acid to the site to be linked into the protein. Various minor types of RNA also exist; at least some act as catalysts (ribozymes), a function long ascribed only to proteins.