The definition I remember being taught early on includes that, so that's on the right track. From memory: 1. Reproduces itself/making things similar to itself

The definition I remember being taught early on includes that, so that's on the right track. From memory: 1. Reproduces itself/making things similar to itself (sort of; viruses are on the periphery, prions...). 2. Metabolizes chemicals for energy 3. to grow, and as a result, 4. produces waste. 5. Reacts to stimuli in the environment. 6. Maintains homeostasis (reacts to stimuli in itself and keeps 1-5 going). I'm probably forgetting some and there are exceptions to all of these. Notably, in interesting cases like at the inception of life, or at the periphery of life: viruses, parasites, potential extraterrestrial chemical systems, and arguably cultural systems. But those criteria are still convenient.