What does the “eco” in eco-friendly mean?

Q. I know that eco-friendly means good for the environment, but what does the “eco” part of “eco-friendly” actually mean?

Adam answers:

“Eco” is a prefix derived from “ecology” or “ecological.”

You have probably long been familiar with words like ecosystem or ecotype that use the prefix, but in more recent years “eco-” has gotten attached to all sorts of words in order to suggest a link to nature and the environment: eco-tourism, Ford’s EcoBoost engine, and, of course, eco-friendly.