Explanation

Quick Answer

An ordinal number (número ordinal), as the name suggests, is a number that indicates the order of a noun that forms part of a series.

Just like cardinal numbers, ordinal numbers are adjectives. But, unlike Spanish cardinal numbers, Spanish ordinal numbers actually do match the nouns they modify in both gender and number. Additionally, ordinal numbers usually come before nouns.

Check out these examples showing Spanish ordinal numbers in use.

examples
Es el segundo carro que he comprado. It is the second car that I have bought.
Los primeros días de nuestras vacaciones fueron fantásticos. The first days of our vacation were fantastic.
Mira la octava página. Look at the eighth page.
Fuimos las primeras personas invitadas a la fiesta. We were the first people invited to the party.

Ordinal Numbers: Primero to Décimo

The ordinal numbers from primero to décimo should be memorized, as they have unique forms and are used to form most of the other ordinal numbers in Spanish.

Here are a list of the ordinal numbers in Spanish from primero (first) to décimo (tenth).

English	Spanish
first	primero
second	segundo
third	tercero
fourth	cuarto
fifth	quinto
sixth	sexto
seventh	séptimo
eighth	octavo
ninth	noveno
tenth	décimo

When they come before nouns that are singular and masculine, primero and tercero are shortened to primer and tercer, respectively.

For example

el primer presidente(the first president)

el tercer capítulo(the third chapter)

Ordinal Numbers: Decimoprimero to Decimonoveno

The teen ordinal numbers are normally written as a single word, and they are formed according to the following formula.

décimo + ordinal number between primero and noveno

For example:

thirteenth: décimo + tercero = decimotercero
fifteenth: décimo + quinto = decimoquinto
seventeenth: décimo + séptimo = decimoséptimo

Note that the accent on décimo is removed in these ordinal numbers.

Here are a list of the ordinal numbers in Spanish from decimoprimero(eleventh) to decimonoveno(nineteenth).

English	Spanish
eleventh	decimoprimeroor undécimo
twelfth	decimosegundoor duodécimo
thirteenth	decimotercero
fourteenth	decimocuarto
fifteenth	decimoquinto
sixteenth	decimosexto
seventeenth	decimoséptimo
eighteenth	decimoctavo
nineteenth	decimonoveno

Notice that decimoctavodoes not follow the above pattern exactly. The o is removed from décimo before adding octavo so that you don’t end up with one o right after another.

Spelling Variations

According to the RAE, it is also acceptable to write the ordinal numbers from decimoprimero to decimonovenoas two separate words.

For example:

thirteenth = décimo tercero
fifteenth = décimo quinto
seventeenth = décimo séptimo

When written as two separate words, both words must agree in gender with any noun they modify. When written as a single word, only the final word in these compounds agrees in gender with the noun.

examples
la decimoprimera página the eleventh page
la décima primera página the eleventh page

Ordinal Numbers Divisible by Ten

Here are a list of the ordinal numbers divisible by 10 that fall between vigésimo(twentieth) and nonagésimo(ninetieth). These are used as the base from which to form all the ordinal numbers between twentieth and ninety-ninth.

twentieth	vigésimo
thirtieth	trigésimo
fortieth	cuadragésimo
fiftieth	quincuagésimo
sixtieth	sexagésimo
seventieth	septuagésimo
eightieth	octogésimo
ninetieth	nonagésimo

Using the formula below, forming the ordinal numbers between twentieth and ninety-ninth is quite easy.

base number (divisible by 10) + ordinal number between primero and noveno

For example:

twenty-first: vigésimo + primero = vigésimo primero
thirty-sixth: trigésimo + sexto = trigésimo sexto
ninety-ninth: nonagésimo + noveno = nonagésimo noveno

Ordinal Numbers Above 100

Below are the ordinal numbers divisible by 100 that fall between centésimo and milésimo.

hundredth	centésimo
two hundredth	ducentésimo
three hundredth	tricentésimo
four hundredth	cuadringentésimo
five hundredth	quingentésimo
six hundredth	sexcentésimo
seven hundredth	septingentésimo
eight hundredth	octingentésimo
nine hundredth	noningentésimo
thousandth	milésimo

For ordinal numbers between 101 and 999, write out each successive ordinal number as a separate word.

For example:

four hundred eighty-second: cuadringentésimo + octogésimo + segundo = cuadringentésimo octogésimo segundo
one hundred seventy-seventh: centésimo + septuagésimo séptimo = centésimo septuagésimo séptimo

Abbreviations

Just like in English, Spanish ordinal numbers are often written in an abbreviated form. To abbreviate Spanish ordinal numbers, you can follow the formulas below.

For masculine ordinal numbers*: numeral + . + superscript o
- *For primer and all numbers ending in primer = numeral + . + superscript er
- *For tercer and all numbers ending in tercer = numeral + . + superscript er
For feminine ordinal numbers: numeral + . + superscript a

examples
1.º 1st
10.ª página 10th page

Placement

In Spanish, ordinal numbers usually go before the nouns they modify. However, if the noun is a member of the royalty, a pope, or a street name, you may see the ordinal adjective come after. For example: