The (subtle?) distinction is around "what it is" rather than "what it is for": A deterministic process always produces the same output given the same set of in

The (subtle?) distinction is around "what it is" rather than "what it is for": A deterministic process always produces the same output given the same set of inputs. A hermetic behavior ensures that indeed you'll always have the same inputs. It can just be a set of best practices (e.g. being very careful of not depending on external inputs that might change outside of your control) or it can involve an active barrier that sandboxes your environment in order to ensure that you indeed always have the same inputs. A reproducible process is a process that can be repeated later in the future. There are various degrees of reproducibility you might be interested in. For example, you might want "bit for bit" reproducibility (important for security) or you just want to make sure you can rebuild something functionally equivalent (e.g. the compilation or link phase might not be fully deterministic in the order and layout of compilation units). Reproducible processes usually rely on a deterministic system and leverage hermetic behaviours to ensure reproducibility (over time or across locations)