"system" denotes something which was designed to work as a whole. Pieces are connected together by a manufacturer to build a system. The operating system is a k

"system" denotes something which was designed to work as a whole. Pieces are connected together by a manufacturer to build a system. The operating system is a kernel, UI, tools, etc taken by a creator and put together into a packaged tool that people can use on their computers. "ecosystem" denotes an environment created by some kind of vessel e.g. Earth, the ocean, Ethereum, etc where independent entities can be created, develop, and compete for resources, attention, space, etc provided by that environment. The entities have no real connection to their environment besides just living within it and interacting with the other entities. Ethereum is just as much of an environment as the Earth is. It provides the foundation which the entities live on top of (security), the resources the entity needs to exist (data availability), and the gathering point where complex interactions can happen (smart contracts and end users). Ethereum doesn't build any of the ecosystem, it simply provides the marketplace where life happens.