Transits
Shadow Period
The degrees a retrograde planet revisits before and after the backward phase.
The shadow period is the span of zodiac degrees a planet will traverse three times during a retrograde cycle: once in pre-shadow, again while retrograde, and a final time in post-shadow. Events or themes often echo across these passes, giving you a preview, a review, and then integration.
Example
During Mercury's pre-shadow you might hear about a contract; the retrograde brings revisions; post-shadow is when it finally gets signed.