What is dihydroretinol?

Some articles on dihydroretinol:

All-trans-retinol 13,14-reductase
... the chemical reaction all-trans-13,14-dihydroretinol + acceptor all-trans-retinol + reduced acceptor Thus, the two substrates of this enzyme are all-trans-13,14-dihydroretinol and acceptor, whereas its two products ... (13,14)-all-trans-retinol saturase, and all-trans-retinolall-trans-13,14-dihydroretinol saturase ...