Evolution of photodynamic therapy and definition of treatments involving light
| Treatment | Definition/component |
| Heliotherapy | Use of sunlight for treatment |
| Phototherapy | Treatment using specific light (e.g. ultraviolet) |
| Photochemotherapy | Treatment using specific light and chemical compound, and nonspecific light, usually in the presence of air/oxygen |
| Photodynamic therapy | Treatment using chemical photosensitising agent (drug) |
| + matching specific wavelength light (laser/nonlaser, i.e. collimated/noncollimated light) | |
| + oxygen (present in living tissue environment) |