1. In psychopathology, this is material abused (e.g. Cocaine, alcohol, marijuana), a medicine (sedative, for example) or toxin; 2. In philosophy this is individualistic, autonomous and exists alone and unchanged even if some of its featured to change because of outer effects.
SUBSTANCE: "Example: Marijuana is substance that contains THC which provokes release of dopamine, which subsequently causes feeling of being "high"."