Across
1
Closed shape with straight sides
5
Space between two intersecting lines
6
Part of a line with two endpoints
7
Longest side of a right triangle
12
Line crossing from corner to corner
Down
2
Exact correspondence on both sides
3
Difference between highest and lowest values
4
Line segment connecting two circle points
8
Single numeral from 0 to 9
9
Rectangular array of numbers
10
The number representing nothing
11
Comparison of two quantities
13
Corner point of a polygon