http://dietary-supplements.info.nih.gov/factsheets/botanicalbackground.asp
Office of Dietary Supplements, National Institutes of Health
A botanical is a plant or plant part valued for its medicinal or therapeutic properties, flavor, and/or scent. Herbs are a subset of botanicals. Products made from botanicals that are used to maintain or improve health may be called herbal products, botanical products, or phytomedicines.