Across
1
Exact correspondence on both sides
2
Lines that never intersect
5
Single numeral from 0 to 9
6
Line touching circle at one point
7
Sum divided by count
8
The number representing nothing
Down
1
Collection of distinct elements
2
U-shaped curve of a quadratic function
3
Repeated addition
4
Power to which a number is raised
9
Three-sided polygon
10
Difference between highest and lowest values
11
Comparison of two quantities
12
System of ordered marks for measuring