Also called partitives, they indicate equal parts of a segmentable whole. They express, therefore, the fraction or part of an element or a set of them. Its designation is based on accounting entities; una mitad, tres octavos, dos cuartos, etc. As in the case of cardinals, the semantic scope of their forms is quantification.
Each fractional adjective has its corresponding noun; una tercera parte de ~ un tercio de.
The grammatical categories that develop these numerals are ADJECTIVES, SUBSTANTIVE AND PRONOUNS.
Unlike other cases examined, in this area of the numerals all academic sources coincide when it comes to exposing their syntactic regime (DRAE, DPD, NGLE §21.6).
As in some of the cases studied, there is the circumstance that certain "own" forms of a block participate in other paradigms of the numerals. As can be seen, several of the partitive forms below the ten coincide with the ordinal forms; Felipe Quinto ~ dos quintos de la población. Unlike the semantic alternation of the cardinals, in which the form belongs to the same ―cardinal― paradigm that is duplicated in full because they exert two different functions ―quantifying and ordinal / identifying―, here only certain forms are duplicated that have a place in both paradigms ―ordinal and fractional― with two different semantic functions ―ordinal / identifying and quantifying― respectively. In summary it is noticed that the masculine forms corresponding to the fraction will coincide with the ordinal nouns below the tenth, while the feminine ones will coincide with the adjectives smaller than the same number. The same happens in centésimo/a milésimo/a, millonésimo/a.
The fractionaries from 2 to 10 are transcribed with special words or terms of the ordinals; medio, tercio, séptimo, noveno... From 1/11 the partitives are constructed with the ending –avo/a that is added to the singular masculine form (apocopated where appropriate) of the corresponding cardinals forming a single word: onceava (part), doceavo, treintaiunava (not *treintaiunoava), dos treintaiunavos (not *dos treintaiunoavos), milesimodoscientosetentaiochoavo, setecientosochentaiseisavo… (DPD, NGLE, OLE, consult Fundéu).
Although the normative proposal maintains the composition of a single word regardless of the amount and length of the figure, authors such as Martínez de Sousa recommend segmentation in the writing of fractions over 100, avoiding the formation of excessively long words. TIP numbers offers both versions. In this way, the application will show for the fractional number 320 786:
Given that the authors who recommend segmentation do not clarify how this applies to multiples of 1000 and multiples of millions, we choose to apply the Spanish Royal Academy's criterion on ordinal numbers in these cases. We thus consider that both milésimo and millonésimo are forms that are not written in isolation but linked to the cardinal number that precedes it:
Dado que los autores que recomiendan la segmentación no aclaran como se aplica ésta a los múltiplos de 1000 y los múltiplos de millón, optamos por aplicar el criterio de la Real Academia Española sobre los números ordinales en estos casos. Consideramos así, que tanto milésimo como millonésimo son formas que no se escriben aisladas sino unidas al número cardinal que le precede: