- periodontalsurrounding a tooth
- perigeeThe point, in an orbit about the Earth, that is closest to the Earth: the periapsis of an Earth orbiter.
- periodontitisA serious form or stage of periodontal disease which may lead to loss of bone and falling out of teeth.
- perinatologyA branch of obstetrics focusing on the medical and surgical management of high-risk pregnancies.
- periosteumA membrane surrounding a bone.
- peri-surrounding
- periastronThe point of an orbit in which a celestial body is at its closest to the star it is orbiting.
- perikronePeriapsis around the planet Saturn.
- peritropalInvolving turning oneself around: rotating or circuitous.