Long non-coding RNA are a type of RNA generally defined as transcripts with more than 200 nucleotides that are not translated into proteins. This arbitrary boundary distinguishes long ncRNAs from small non-coding RNAs, microRNAs (miRNAs), small interfering RNAs (siRNAs), Piwi-interacting RNAs (piRNAs), small nucleolar RNAs (snoRNAs), and other short RNAs. Long intervening/intergenic noncoding RNAs (lincRNAs) are sequences of lncRNAs that do not overlap with protein-coding genes.
Long noncoding RNAs include intergenic lincRNAs, intronic ncRNAs, and sense or antisense lncRNAs, each type having different genomic positions relative to genes and exons.