I have absolute copy number data for a diploid organism. I would like to distinguish between a Gain and an Amplification. I am currently using the term Gain to define any chromosomal copy number increase from the norm - in this case 2. I would like to know if anyone has an arbitrary absolute copy number cut-off to distinguish between a Gain and and Amplification. For example, would you consider it to be a copy number greater than say copy number 4?