There are multiple definitions:

1. outpatient(English)

   • IP, OPD
   • Patient care

2. occipitoposterior position(English)

   • Obstetrics

3. osmotic pressure(English)

   • Physiology

4. ouderdomspensioen(Dutch)

   • IP, NP
   • Financial issues, Aging

5. osteoporosis(English)

   • there are shared biological mechanisms and functional genetic determinants with RA
   • BMD, cFDR, CRV, eBMD, eQTL, FN-BMD, GWAS, LS-BMD, T2DM, WGCNA, RA, SNP
   • Aging, Genomics
   • https://doi.org…223-021-00817-4

6. organophosphate [ester](English)

   • a pesticide pointing to the importance in understanding the toxicity and the application to risk assessment
   • AChE, BuChE, CB, ChE, NTE, OPIDN
   • Toxicology
   • https://doi.org…74367-1.00068-9

7. open posterior(English)

   • refers to lumbar fusion in treatment of lumbar spondylolisthesis
   • EBL, MI
   • Surgery, Spine (or spinal cord)
   • https://doi.org…55/2017/8423638

8. occiput posterior(Latin)

   • position that is associated with adverse maternal and neonatal outcomes
   • OA, OT
   • Obstetrics, Neonatology, Pregnancy
   • https://doi.org…gmf.2021.100346

9. orange pulp(English)

   • SH
   • Diet, Veterinary medicine
   • https://doi.org…al.pone.0151215

10. organophosphorus(English)

    • refers to nerve agents [so-called G-agents] such as tabun, sarin, soman and VX
    • CEES, CWA, CWC, DDGel, DEF, DIMP, MPEG2, RSDL, SC, SM, WMD
    • Toxicology, Military medicine
    • https://doi.org…0975-7406.68498

11. organizing pneunomia(English)

    • CTD, DM, ILD, MCTD, NSIP, PM, UCTD
    • Pulmonology, Infection
    • https://doi.org…55/2021/5536360