What is the difference between a competitive endogenous RNA and an ncRNA in an ncRNA-miRNA-mRNA axis? Or are they just similar?

.a a lot of papers have described competitive endogenous RNA (ceRNA) as noncoding transcriptome that competes with mRNA for miRNA. Theoretically, overexpression of one of these counterparts will intensify its effect over the other. For instance, If a long non-coding RNA that competes with mRNA “PROTEIN” for miRNA... show more .a a lot of papers have described competitive endogenous RNA (ceRNA) as noncoding transcriptome that competes with mRNA for miRNA. Theoretically, overexpression of one of these counterparts will intensify its effect over the other. For instance, If a long non-coding RNA that competes with mRNA “PROTEIN” for miRNA “x” is overexpressed, it will attenuate miRNA x’s silencing regulation on mRNA “PROTEIN”; thus, indirectly upregulate"PROTEIN".so, wouldn't any ncRNA in a regular ncRNA-miRNA-mRNA axis be considered a ceRNA,or is their any further characterization of ceRNAs ?
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