Relating to tides.
From tide + -al. Probably a hybrid formation within English. Alternatively it might be from an unattested British Medieval Latin *tīdālis, derived from rare tīda, from Old English tīd. The usual Latin word for “tidal” is aestuālis.
Oefen met het spreken en memoriseren van " tidal " en vele andere woorden en zinnen in Engels .