What is Acceptable Daily Intake?

Legal Definition
Acceptable daily intake or ADI is a measure of the amount of a specific substance (originally applied for a food additive, later also for a residue of a veterinary drug or pesticide) in food or drinking water that can be ingested (orally) on a daily basis over a lifetime without an appreciable health risk. ADIs are expressed usually in milligrams (of the substance) per kilograms of body weight per day.
-- Wikipedia
Legal Definition
This is the maximum amount of any material that a person can be exposed to over their lifetime without being harmed. The ADI is measured in milligrams of the substance, per kilogram of body weight of the exposed person, per day (mg/kg/day). Refer to the definition to reference dose.