1. Ordinal Numbers
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2. Ordinal numbers can also be called place value numbers
Ordinal numbers can also be called place value numbers. In English, an example is first, second, third.
The ordinal numbers come before the noun and must agree in gender.

3. The Spanish Ordinal Numbers
First-primero/a
Eighth-octavo/a
Second-segundo/a
Ninth-noveno/a
Third-tercer/a
Tenth-décimo/a
Fourth-cuarto/a
Fifth-quinto/a
Sixth-sexto/a
Seventh-séptimo/a

4. Special Rules
When you have a masculine noun following the words first and third, you need to drop the –o.
Ex. El primer chico-the first boy
El tercer escritorio-the third desk