From early on in stats education, you get the difference between statistics and parameters drilled into your head. However, I've more recently (outside of school) encountered the term "metric," and I've begun using it a lot myself. (e.g. talking about developing a metric for gauging timely processing)
my actual question: What is the appropriate way to use the term "metric," and how is its meaning different from "statistic" and different from "parameter"?