Strong’s Greek
G2785 — ketos
The entry below is Strong’s own definition (1890, public domain), and every verse where the word occurs.
κῆτος
ketos — pronounced kay'-tos
probably from the base of 5490; a huge fish (as gaping for prey):--whale. see GREEK for 5490
1 occurrence in the KJV.
Matthew 12:40
For as Jonas was three days and three nights in the whale’s belly; so shall the Son of man be three days and three nights in the heart of the earth.