It means the distance from the center of a circle out to its curvy part.
A line that bisects a circle and goes through the center of it is the diameter.
The place of 0o , in the very center, the origin on a coordinate plane, line, etc.
principal(in terms of math)- the amount you borrow or deposit
HL in math mean hypotenuse leg
ask your math teacher
the center in Math means that all the points on the outside of the circle go to the center of the cirlce
sum means the answer of a math problem
A number? ^^