The augur was a priest and official in the classical Roman world. His main role was the practice of augury, interpreting the will of the gods by studying the flight of birds: whether they are flying in groups or alone, what noises they make as they fly, direction of flight and what kind of birds they are. This was known as "taking the auspices." The ceremony and function of the augur was central to any major undertaking in Roman society—public or private—including matters of war, commerce, and religion. The Roman historian Livy stresses the importance of the augurs: "Who does not know that this city was founded only after taking the auspices, that everything in war and in peace, at home and abroad, was done only after taking the auspices?" Although ancient authors believed that the term "augur" contained the words avis and gero—Latin for "directing the birds"—historical-linguistic evidence points instead to the root aug-: "to increase, to prosper."