Definition:
Abstinence is when a person does not take any substances of abuse. A person abstains from the use of alcohol, illicit drugs and other addictions. Examples of other addictions include, but are not limited to, smoking, eating disorders, gambling, and self-harm.
The term clean usually refers to being abstinent from substances other than alcohol, whereas the term sober usually refers to being abstinent from alcohol. Clean and sober means abstinent from both.
When a person is prescribed a medication or is on Medication-Assisted Treatment (MAT), such as methadone, and takes it as prescribed, they are considered abstinent from substances of abuse.