| A | B |
| circuit | a revolving; a journey around a route |
| circulatory | going in a circuit, circular |
| circumnavigate | to sail around |
| circumstance | the condition surrounding or related to an event |
| circumvent | to go around or bypass |
| period | interval between certain |
| periodic | happening at regular intervals; happening from time to time |
| perigee | the point in the moon's or a satellite's orbit that is closet to the earth or body it is orbiting |
| periphery | the outer boundary of something |
| periscope | an instrument for seeing around things |
| cir, circum | around |
| peri | around, surrounding, near |