What is The is the basic unit of?

Answer 1

Possibly the most familiar to many people is degrees, but this is not the only unit. Radians are a unit often easier to work with.

A full circle = 360 degrees = 2pi radians.

It could be argued radians are a more basic unit since they're based on the formula for circumference and not on dividing the circle into an arbitrary number of pieces - someone had to choose 360 rather than 400, 1000, or some other number for number of degrees in a circle.

... The 360 comes from the Babylonians, ca 1500BC. Their number system was based on 60 (6X60=360) - this is also the reason for 60 minutes in an hour and 60 seconds in a minute, in angles as well as time.