Herbal formulas will generally be selected for their intended influences (or "functions") first, their TCM patterns second, and for their use with certain symptoms third or not at all. Practitioners of TCM are generally more focused on treating the root vs. the symptoms and the gem of Chinese Medicine, by most accounts, is the diagnostic framework which helps a practitioner to tailor every approach, consistently, to each individual.
Formulas are often used in stages of treatment (i.e. they are often intended to be changed/alterated in most cases over the course of treatment). The functional categories below are some of the more common groupings to help guide the overall treatment approach.