RPKM is reads per kilobase of coding sequence per million mappable reads, which represents gene/isoform expression level.
CV is abbreviated from coefficient of variation, which stands for the fluctuation of gene/isoform expression levels across tissues.
Length of isoform: Long: length>500bp, Medium: 100bp<length≤500bp, Short: 20bp≤length≤100bp.
Expression level of isoform: High: RPKM>100, Moderate: 10<RPKM≤100, Low: RPKM≤10. If isoforms expressed differentially in different tissues or cell lines, the highest expression level is considered.