a nucleic acid that is an essential component of all cells, composed of a long, usually single-stranded chain of nucleotide units that contain the sugar ribose; ribonucleic acid
See RNA in American Heritage Dictionary 4
(ärˌĕn-āˈ)
noun
A polymeric constituent of all living cells and many viruses, consisting of a long, usually single-stranded chain of alternating phosphate and ribose units with the bases adenine, guanine, cytosine, and uracil bonded to the ribose. RNA molecules are involved in protein synthesis and sometimes in the transmission of genetic information. Also called ribonucleic acid.