## Ordinal Numbers (to Billionth)

### Ordinal Numbers: Learn

Ordinal numbers are important in multiple areas. The first use of ordinal numbers
is to describe the order of objects, often written in the "figure" form.
Another is to name exponents (e.g. 2^{5} is "two to the *fifth* power").
Ordinal numbers are also used to name the denominators in fractions,
often written in "full-word" form (e.g. one-third, three-fifths, six-tenths).

When ordinal numbers are written as figures the last two letters of the written ordinal are added to the cardinal number. Both the figure and the full-word formats are shown below.

- 10th Tenth
- 20th Twentieth
- 30th Thirtieth
- 40th Fortieth
- 50th Fiftieth
- 60th Sixtieth
- 70th Seventieth
- 80th Eightieth
- 90th Ninetieth
- 100th One Hundredth
- 1000th One Thousandth
- 1000000th One Millionth
- 1000000000th One Billionth

### Ordinal Numbers: Practice

#### What is the name of the given numeric ordinal?

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