| OIF | observed intrinsic frequency; oil immersion field; Osteogenesis Imperfecta Foundation |
|---|---|
| PRF | partial reinforcement; patient report form; perforin; plasma recognition factor; pontine reticular f... |
| PSIL | preferred frequency speech interference level |
| Rf | respiratory frequency; rutherfordium |
| SFD | silo filler's disease; skin-film distance; small for dates; spectral frequency distribution |