Crossword clue: a prefix, from the latin re and ad combined, coming to us through the french and italian. see re-, and ad-.

The most common answer is ra (2 letters).

1 answer found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

Possible answers

ra 2 letters web-def

(astronomy) the equatorial coordinate specifying the angle, measured eastward along the celestial equator, from the vern