Wikipedia - Herbalism http://en.wikipedia.org/wiki/Herbalism
NaturalRemedies.org http://www.naturalremedies.org
US National Institutes of Health / National Library of Medicine
MedlinePlus Health Topics https://medlineplus.gov/healthtopics.html
World Health Organization (WHO) Health topics https://www.who.int/health-topics/
CDC Diseases & Conditions A-Z Index https://www.cdc.gov/diseasesconditions/index.html
WebMD Common Health Topics https://www.webmd.com/a-to-z-guides/common-topics
WHO International Classification of Diseases https://icd.who.int/en
Encyclopædia Britannica Classifications of diseases from the article human disease https://www.britannica.com/science/human-disease/Classifications-of-diseases
(Subscription only, free article with adds)
Encyclopedia Galactica 117th Edition, 1026 F.E. Link not available at the time of writing