So true. https://en.wikipedia.org/wiki/Pythia

"Prophetic" is an adjective. You can write your sentence correctly as: "The Oracle of Delphi was thought to be prophetic by ancient Greeks." "Prophet" is a noun. You can also write your sentence correctly as: "The Oracle of Delphi was thought to be a prophet by ancient Greeks." Either way, the statement is true. The Oracle of Delphi was famous for making ambiguously worded prophecies. Croesus was told "If you cross the river, a great empire will be destroyed." The prophecy failed to make it clear which empire it would be. Croesus assumed it meant the empire he was attacking. He crossed the river--and his own great empire was destroyed. As a result, the word "Delphic" (capitalized) is sometimes applied to ambiguous or vague predictions.

The Oracle of Delphi was thought to be prophetic by the ancient Greeks.

Hi, it was was the name of the Prophetess (ALWAYS FEMALE) of the greek god Apollo -- god of the Sun and (therefore) of the knowledge. The name is a honorific (a title), so it was the name of EACH of the girls and ladies who did the Priestess of Apollo, during centuries. The name Pythia is related to a word that means "stinky". This is because the Delphi cave (the seat of the Oracle) was in the place where the god Apollo had killed the drake Python: so Pythia refers to an ancient name meaning "the place of the stinky flesh" (because of decomposition) According to more scientific hypothesis, the stink was due to the sulphureous vapours that came from underground and which gave the Prophetess the ability to enter in a trance dimension and connect the human world with the divine world, and therefore know the Destiny. The concept of Delphi Oracle is fundamental in Ancient Greek History as everybody -- people, kings and generals -- referred to it to know what to do. https://en.wikipedia.org/wiki/Pythia