'Courses' in the Bible

From heaven fought the stars, from their courses they fought against Sis'era.

And he sent them to Lebanon, ten thousand a month by courses; a month they were in Lebanon, two months at home; and Adoniram was over the levy.

And David divided them into courses according to the sons of Levi: Gershon, Kohath, and Merari.

and for the courses of the priests and the Levites, and for all the work of the service of the house of Jehovah, and for all the instruments of service in the house of Jehovah:

And behold, the courses of the priests and the Levites are for all the service of the house of God; and thou hast with thee for all manner of workmanship every willing man, skilful for every sort of service; and the princes and all the people are wholly at thy commandment.

And it came to pass when the priests were come out of the holy place (for all the priests that were present were hallowed without observing the courses;