Book 7
10
An odd-times odd number is that which is measured by an odd number according to an odd number.
11
11
A prime number is that which is measured by an unit alone.
12
12
Numbers prime to one another are those which are measured by an unit alone as a common measure.
13
13
A composite number is that which is measured by some number.
14
14
Numbers composite to one another are those which are measured by some number as a common measure.
15
15
A number is said to multiply a number when that which is multiplied is added to itself as many times as there are units in the other, and thus some number is produced.
16
16
And, when two numbers having multiplied one another make some number, the number so produced is called plane, and its sides are the numbers which have multiplied one another.
17
17
And, when three numbers having multiplied one another make some number, the number so produced is solid, and its sides are the numbers which have multiplied one another.
18
18
A square number is equal multiplied by equal, or a number which is contained by two equal numbers.
19
19
And a cube is equal multiplied by equal and again by equal, or a number which is contained by three equal numbers.
20
