In both Spanish and English, there’s a lot of overlap between fractions and ordinals: the vast majority of these two types of numbers share the same word. In English, they are identical from "third" on up, while in Spanish they’re the same starting with cuarto.
|a third||1/3||un tercio|
|a fourth||1/4||un cuarto|
|a fifth||1/5||un quinto|
|a sixth||1/6||un sexto|
|a seventh||1/7||un séptimo|
|an eighth||1/8||un octavo|
|a ninth||1/9||un noveno|
|a tenth||1/10||un décimo|
Most Spanish fractions up to décimo are similar to their corresponding cardinal numbers but as you can see in the list above, there is no consistent method for creating them.
Starting at onceavo, that changes: you can create fractions by adding –avo to the cardinal number:
|an eleventh||1/11||once||un onceavo|
|a twelfth||1/12||doce||un doceavo|
|a twentieth||1/20||veinte||un veinteavo|
|a thirtieth||1/30||treinte||un treinteavo|
This works up to but not including one hundredth (1/100), which is un centésimo.
Spanish has two words for "half":
1) la mitad (de) (noun)
|la mitad de los estudiantes||half of the students|
|Compré una pizza anoche y comí la mitad.||I bought a pizza last night and ate half (of it).|
2) medio (adjective)
Medio has a feminine form, media, but no plural forms: it can be used only with singular nouns.
|Quiero un medio bocadillo.||I want half a sandwich.|
|Hay media manzana en la mesa.||There’s half an apple on the table.|
Other than la mitad and medio/media, all Spanish fractions are masculine and must be preceded by a number. When it’s more than one, the fraction is plural:
When fractions are used with the feminine noun parte, they act as adjectives and thus change to agree with it:
|una tercia parte||a third|
|una octava parte||an eighth|
|tres décimas partes||three tenths|
When any fraction other than medio is followed by a noun, the preposition de is needed as a go-between.
|3/4 of the students||tres cuartos de los estudiantes|
|2/5 of the book||dos quintos del libro|
Spanish fractions and ordinal numbers are abbreviated differently. The fraction un quinto can only be abbreviated 1/5, whereas the ordinal el quinto is shortened to 5o.
Beginning with "fourth," Spanish fractions are identical to ordinal numbers, other than the type of article:
- a fourth = un cuarto
- the fourth = el cuarto