General Sense:
* Artificial: This suggests something man-made or not naturally occurring.
* Non-natural: This emphasizes the absence of nature.
* Unnatural: Similar to "non-natural" but with a stronger implication of being contrary to nature.
* Inner world: This contrasts with the external environment and focuses on the internal thoughts and feelings.
Specific Contexts:
* For "physical environment": *Inner space*, *personal space*, *artificial space*, *built environment*.
* For "social environment": *Isolation*, *solitude*, *alienation*.
The best antonym for "environment" will depend on the specific context in which you are using the word.