Any functional RNA molecule that is not translated into protein. Noncoding RNAs include ribosomal RNA (rRNA); transfer RNA (tRNA); various forms of small ncRNA that are involved in RNA interference, such as short interfering RNA (siRNA), micro RNA (miRNA), and piwi-interacting RNA; small nuclear RNA (snRNA) and small nucleolar RNA (snoRNA); long noncoding RNA; and transfer-messenger RNA.