1.NounA set of labels applied to the various objects in a system, to packaged goods, and so on; the act or process of applying them.
"The labeling is required to include the nutrition facts itemized in 21 CFR 101.9."
2.NounThe introduction of a traceable chemical group (e.g., containing an isotope or a fluorescent dye) into a protein or other biomolecule of interest so it can be tracked or quantified during experimental analysis.