'Service' in the Bible

young men in whom there was no physical defect and who were handsome, well versed in all kinds of wisdom, well educated and having keen insight, and who were capable of entering the king's royal service -- and to teach them the literature and language of the Babylonians.

The king assigned them fine food and choice wine on a daily basis, ordering them to be trained for three years, at the end of which time they would enter the king's service.

The king talked with them, and out of them all not one was found like Daniel, Hananiah, Mishael and Azariah; so they entered the king’s personal service.

So Daniel remained there in service until the first year of King Cyrus.