Atom-tagging is a process of labeling or marking atoms for identification purposes. Synonyms for this term could include atom labeling, atom marking, atom tracing, or atom tracking. These phrases all essentially describe the same process of assigning a unique identifier to atoms in order to keep track of them in a system or experiment. Other potential synonyms could include atom coding, atom identification, or atom signature. Ultimately, the key to understanding the various synonyms for atom-tagging is to recognize that they all relate to the idea of differentiating one atom from another for analytical or experimental purposes.