Across
1
Line crossing from corner to corner
4
The number representing nothing
6
Value that does not change
7
Number less than zero
8
Lines that never intersect
Down
2
Amount of space an object occupies
3
Total distance around a shape
5
Space between two intersecting lines
9
Number divisible only by 1 and itself
10
Number with digits after a point
11
Collection of distinct elements