回複：relinkd ?= PD carry over ? confused

Not quite. relink can mean anything about switching your eligibility category basis of a pending I485. You can have many I-130s, I-140s, other immigration petition (over 100 types of eligibility categories) and you can also be derivative to your spouse's many petition types. Or if under 21, to your parents' many petitions,.. theoretically thousands of possible scenarios of relink.

PD carry-over is just one of the many scenarios of "relink", it is based on the same person's two (or more) approved I-140s.