Quick answer
el primer día · la segunda vez
They agree like adjectives, and primero and tercero lose their -o before a masculine noun.
One to ten
| Number | Ordinal | English |
|---|---|---|
| 1 | primero / primera | first |
| 2 | segundo / segunda | second |
| 3 | tercero / tercera | third |
| 4 | cuarto / cuarta | fourth |
| 5 | quinto / quinta | fifth |
| 6 | sexto / sexta | sixth |
| 7 | séptimo / séptima | seventh |
| 8 | octavo / octava | eighth |
| 9 | noveno / novena | ninth |
| 10 | décimo / décima | tenth |
primer and tercer
Before a masculine singular noun these two drop the final -o. The feminine forms stay whole.
Standing alone the full form comes back: Soy el primero.
Above ten, and with names
From eleven onwards the cardinal number is normal, and it follows the noun. Kings and popes take ordinals up to ten, cardinals after that.
Abbreviations use a raised letter: 1.º, 1.ª, 3.er.
Memory trick
Ordinal numbers are adjectives, so they agree. Only primero and tercero shorten, and only before a masculine singular noun.
Typical mistakes
el primero día del curso
el primer día del curso
Before a masculine singular noun primero loses its -o.
Es la tercer vez.
Es la tercera vez.
The shortening only happens in the masculine. The feminine keeps tercera.
Vivo en el doceavo piso.
Vivo en el piso doce.
Doceavo is a fraction. For floors above ten Spanish uses the cardinal number after the noun.
Check yourself
Es el ___ día de mis vacaciones.