In the third year of Cyrus king of Persia a word was revealed to Daniel, whose name was called Belteshazzar; and the word was true, and it was about a great conflict. And he understood the word, and had understanding of the vision.
“third year of Cyrus king of Persia.” Therefore 536/535 BC.
“word.” This is the biblical use of “word” as a message, not just a single “vocabulary word.” Christians typically use this jargon today, such as, “I have a word [message] from the Lord.”