First, Second, etc.: Ordinal Numbers

Here are the ordinal numbers first through tenth:

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

The ordinal numbers are adjectives and so their endings depend on the gender and number of the noun they are describing. Unlike most adjectives, they usually come before the noun:

la segunda puerta	the second door
su cuarto poema	his fourth poem

Remember that although poema ends in -a, it is a masculine noun (el poema).

The masculine forms of primero and tercero drop the -o when preceding a noun:

nuestro primer hijo	our first child
el tercer elemento	the third element

When primero or segundo begin part of a series preceding a noun, dropping the -o is optional:

• nuestros primer(o) y tercer hijos    our first and third children

Ordinal numbers beyond décimo (tenth) are rarely used. Often, the cardinal number is substituted:

• el siglo dieciocho the eighteenth century

At other times, speakers word the sentences to avoid needing to use the ordinal number: 

• él cumple diez años    he is having his tenth birthday

Although there is no need to memorise them, here is a list of some ordinal numbers beyond décimo:

eleventh	undécimo
twelfth	duodécimo
thirteenth	decimotercero
forteenth	decimocuarto
fifteenth	decimoquinto
sixteenth	decimosexto
seventeenth	decimoéptimo
eighteenth	decimoctavo
nineteenth	decimonoveno
twentieth	vigésimo
twenty-first, etc.	vigésimo primero, etc.
thirtieth	trigésimo
fortieth	cuadragésimo
fiftieth	quincuagésimo
sixtieth	sexagésimo
seventieth	septuagésimo
eightieth	octogésimo
ninetieth	nonagésimo
hundredth	centésimo
two hundredth	ducentésimo
three hundredth	tricetésimo
four hundredth	cuadringentésimo
five hundredth	quingentésimo
six hundredth	sexcentésimo
seven hundredth	septingentésimo
eight hundredth	octingésimo
nine hundredth	noningentésimo
thousandth	milésimo
two thousandth	dosmilésimo
three thousandth	tresmilésimo