The ROOT-WORD is the Prefix PERI meaning AROUND. As usual, every word opens not only one door, but many doors. This one PERI is no exception. On your list are words useful in medicine, anatomy, geology, mathematics, dentistry, publications, and, of course, space science. In the last, especially, I have been helped by the words PERI & AROUND and APO & AWAY. I used to be confused be PERIgee and APOgee. I couldn’t remember which was far from the sun, which near. Now I know.
1. Pericarp : PERI carp (per’ i karp) n.
Around the fruit; the covering skin or shell
2. Pericentric : PERI centric (per i sen’ trik) adj.
Deposited around the centre
3. Periclitate : PERI clitate (pe rik’ lit ate) v.
To expose to danger
4. Pericranium : PERI cranium (per i kray’ nee um) n.
Around the skull
5. Pericardium : PERI cardium (per i kard’ ee um) n.
Around the heart
6. Periosteal : PERI osteal (per ee os’ tee al) adj.
Situated around the bone
7. Perigee : PERI gee (per’ i jee) n.
That point in the orbit of a satellite nearest to the earth
8. Perihelion : PERI hellion (per i hele’ yon) n.
That point in the orbit of a comet or a planet nearest to the sun
9. Perigon : PERI gon (per’ i gon) n.
An angle that is round
10. Perimeter : PERI meter (pe rim’ et er) n.
The distance around a closed plane figure
11. Perinephritis : PERI nephritis (per i ne frie’ tis) n.
Inflammation of the tissues around the kidneys
12. Period : PERI od (per’ ee od) n.
A period of time ( a going around)
13. Periodic : PERI odie (per ee od’ ik) adj.
Occurring at regular, stated times
14. Periodical : PERI odical (per ee od’ i k’l) n.
A publication which appears in regular intervals
15. Periodicity : PERI odicity (per ee o dis’ it ee) n.
The quality of recurring regularly
16. Periodontal : PERI odontal (per ee o don’t’ al) adj.
Around the tooth
17. Periotic : PERI otic (per ee ote’ ik) adj.
Around the ear
18. Peripatetic : PERI patetic (per i pa tet’ ik) adj.
Walking around; itinerant
19. Periphery : PERI phery (pe rif’ e ree) n.
A line around a surface; as, the circumference of a circle
20. Peripheral : PERI pheral (pe rif’ e ral) adj.
Relating to the periphery