Across
1
Distance from center to edge of circle
3
The number representing nothing
6
Line segment connecting two circle points
7
Total distance around a shape
8
Lines that never intersect
10
Round shape with all points equidistant
11
Number less than zero
Down
2
Mathematical rule or equation
4
Middle value in an ordered dataset
5
Number divisible only by 1 and itself
7
Number greater than zero
9
System of ordered marks for measuring
12
Power to which a number is raised
13
Collection of distinct elements