The Lesson
The denominator is the number written below the line of a fraction.The denominator of this fraction is 4. (The number above the line is called the numerator. It is 1 in the fraction above).
Dictionary Definition
The Oxford English Dictionary defines the denominator as "The number written below the line in a vulgar fraction, which gives the denomination or value of the parts into which the integer is divided."Examples of Denominators
The denominator of the fraction ^{2}/_{3} (twothirds) is 3. The denominator of the fraction ^{5}/_{7} (fivesevenths) is 7.What Does the Denominator Mean?
A fraction is a part of a whole number. The denominator tells you how many equal parts the whole is divided into. (The numerator tells you how many parts of the whole number there are).Visualizing the Denominator
Thinking of slices of a cake is a useful way of visualizing the denominator. A fraction is a part of a whole number. So it can be visualized as a number of slices of cake, which are parts of the whole cake. The denominator tells you how many slices the cake is cut into:
A denominator of 1 means the cake is left whole.

A denominator of 2 means the cake is cut into 2 equal slices.

A denominator of 3 means the cake is cut into 3 equal slices.
What Is a Fraction?
A fraction is a part of a whole number. Fractions consist of a numerator and a denominator. There are three different types of fractions:Fractions with Larger Denominators Are Smaller
If fractions have the same numerator, having a larger denominator makes the fraction smaller.If you visualize the denominator as the number of slices a cake is cut into, then having a larger denominator means:
 having more slices.
 each slice getting smaller.
(If the numerator is the same, then the number of slices we are considering stays the same).