The terms that make up this subgroup are characterized by determining the place occupied by a unit within a series. As in the case of cardinals, it is a conceptually unlimited repertoire, not in morphological or formal terms.
The semantic scope of these units is not related to quantification, but to the identification of the referent within a sequence. They are, therefore, semantically and syntactically compatible with the cardinals; los primeros dos años..
The number of grammatical categories that develop this set of numerals fluctuates -more than in the rest of the numerals- depending on the source that is consulted. In the DRAE all the ordinals are cataloged in the first instance as adjectives, although many of them present the possibility of being used and / or analyzed as nouns. There does not seem to be a systematic criterion to receive this second cataloging; thus, while in the case of a third party, its use as a noun is accepted, in the fifth this function is not recognized. However, if we go to other sources such as the NGLE, the scope of ordinals is extended, including adverbs in this class (§21.4c). The DPD homogeneously extends the range to pronouns and adverbs, although it does not include the possibility of an ordinal substantive use.
The categories that will be recognized in the TIP Lexicon as capable of carrying the semantic label of 'ordinality' will be those of ADJECTIVE, PRONOMBRE, SUBSTANTIVE and ADVERBIO.
Unlike the previous ones, all the ordinal forms have flexion of both gender and number. Obviously, it is excepted to the adverbial category, which is invariably presented in its canonical form.
From 1.º to 10.º present simple forms: first, second, third, etc. For the tens it is used the –gésimo ending as in vigésimo, trigésimo, quincuagésimo. The cero form is not included in any ordinal paradigm, since this number does not indicate any position.
The primero and tercero masculine forms adopt the primer and tercer apocopated variants when being adjectives precede the name. As is logical, this trend extends to the compound ordinals in which primero and tercero are part: vigesimotercer capítulo.
In the hundreds the ending is –centésimo or –gentésimo as in centésimo, ducentésimo, octingentésimo, etc. while the ordinals corresponding to mil, diez mil, cien mil and un millón are, respectively, milésimo, diezmilésimo, cienmilésimo and millonésimo.
The words that form the ordinals between the 13.º and the 29.º can be written together or segmented; decimotercero or décimo tercero; vigesimonoveno or vigésimo noveno; both options will be recognized. The rest of the ordinals is obtained from the juxtaposition of simple forms, which maintain their segmentation in writing, according to the RAE norm. However, there is a tendency to prosodic and morphological cohesion, as in the case of the cardinals, to form with a single term the ordinals from 30 to 99. Thus, the ordinal corresponding to 46.º admits cuadragésimo sexto or cuadragesimosexto.
It is common, for the difficulty for the speaker the formation of ordinal constructions, to find expressions in which a partitive term is used instead of the ordinal. *Treceavo aniversario, *Quinceava edición. This combination, which is inadequate according to the criteria of the NGLE, will not be considered legitimate in the TIP lexicographical repertoire.