High Quality Content by WIKIPEDIA articles! Long non-coding RNAs (long ncRNAs, lncRNA) are generally considered (somewhat arbitrarily) as non-protein coding transcripts longer than 200 nucleotides. This limit is due to practical considerations including the separation of RNAs in common experimental protocols. Additionally, this limit distinguishes long ncRNAs from small regulatory RNAs such as microRNAs (miRNAs), short interfering RNAs (siRNAs), Piwi-interacting RNAs (piRNAs), small nucleolar RNAs (snoRNAs) etc.