There are multiple definitions:

1. polycystic ovary(English)

   • PCOS
   • Gynecology

2. posterior capsule opacification(English)

   • one of the most common complications of cataract surgery, and there is an urgent need to reduce its incidence. Its main treatment, neodymium:YAG (Nd:YAG) laser posterior capsulotomy, may be associated with significant morbidity and is expensive
   • Ophthalmology, Laser technique
   • https://doi.org…6420(99)00506-0

3. photocatalytic oxidation(English)

   • AC, BTEX, CADR, CFM, DBD, EPA, ESP, HEPA, IAQ, PCO, SOA, SP, SVOC, TCO, TVOC, UV, UV-C, UVGI, VOC
   • Air pollution, Preventive medicine
   • https://doi.org…env.2011.05.041

4. posterior condylar offset(English)

   • may refer to anteroposterior femorotibial translation
   • ROF, TKA
   • Skeleton and bone (formation), Knee
   • http://pubmed.n…h.gov/21351608/