Wiktionary
copy number
n. 1 (context genetics English) The number of copies of a gene or plasmid within a cell's genome. 2 (context library science English) The identification number assigned to a specific copy of a work.
Usage examples of "copy number".
He even began to wish that he could at least still talk to the harmless, stupid Matter-Copy Number Five.
All you've been doing is visiting the environment you'd prepared for Copy number five.