correlation between the outcome and the resources used
a measure of the utilization of resources to realize a given objective
Note 1 to entry: An activity is efficient if it minimizes the use of resources, or produces better performance with the same resources.
[SOURCE: ISO 11620:2014, definition 3.16]ISO 5127:2017(en), 3.1.3.04
output work divided by input work
[ ISO 15551-1:2015 (en), 3.45]