A line is a particular set of points.

There is an infinite number of points on a line; there are also infinitely many points between any two distinct points of a line. A line is uniquely determined by any two distinct points, e.g. by points A and B.

The set of points which contains points A and B and all points of the line between these two points is called a line segment. There is an infinite number of points on a line segment.

There are infinitely many points contained in a line and there is also an infinite number of points contained in any line segment.

Although a line extends infinitely in two directions while a line segment is contained between two distinct points on a line, the number of points in a line is not greater than the number of points in a line segment.

a + b = c

a - b = d

a · b = e

a ÷ b = f

a added to b gives c. 

The operation is called addition.

b subtracted from a gives d.

The operation is called subtraction.

a multiplied by b gives e.

The operation is called multiplication.

a divided by b gives f.

The operation is called division.

Numbers may be so arranged in a square that each row, column and diagonal will add up to the same total. Squares of this kind are known as magic squares.