In energy economics and ecological energetics, energy return on investment, also sometimes called energy returned on energy invested (ERoEI), is the ratio of the amount of usable energy (the exergy) delivered from a particular energy resource to the amount of exergy used to obtain that energy resource.
Return on marketing investment, or marketing return on investment, is the contribution to profit attributable to marketing (net of marketing spending), divided by the marketing 'invested' or risked.