Pitman's Commercial Spanish Grammar (2nd ed.)

 Primero[63]               1st   Décimo sexto, etc.       16th 
 Segundo                   2nd   Vigésimo                 20th 
 Tercero                   3rd   Trigésimo                30th 
 Cuarto                    4th   Cuadragésimo             40th 
 Quinto                    5th   Quincuagésimo            50th 
 Sexto                     6th   Sexagésimo               60th 
 Séptimo (Sétimo)          7th   Septuagésimo             70th 
 Octavo                    8th   Octogésimo               80th 
 Noveno (Nono)             9th   Nonagésimo               90th 
 Décimo                    10th  Centésimo               100th 
 Décimo primero, Décimo          Ducentésimo             200th 
   primo, Undécimo,              Tricentésimo            300th 
   Onceno                  11th  Cuadrigentésimo         400th 
 Décimo segundo, duodécimo,      Quingentésimo           500th 
   Doceno                  12th  Sexcentésimo            600th 
 Décimo tercero, décimo          Septingentésimo         700th 
   tercio, Treceno         13th  Octingentésimo          800th 
 Décimo cuarto,                  Novingentésimo          900th 
    catorceno              14th  Milésimo              1,000th 
 Décimo quinto,                  Millonésimo       1,000,000th 
   quinceno                15th  Postrero, ultimo         Last 

Footnote 63: Ordinal adjectives agree in gender and number with the noun they accompany or for which they stand. Final o changes into a for the feminine, and the plural is formed by adding s.

"Primero," "tercero," and "Postrero" drop the O before a masculine noun singular,[64] as --

El primer pedido: The first order.
El tercer lote: The third lot.
El postrer envío: The last shipment.

But --

La primera entrega (fem.): The first delivery.

Footnote 64: Eight words in all present this peculiarity, viz., uno, alguno, ninguno, bueno, malo, primero, tercero, postrero (these last two not always).

After "vigésimo" ordinal numbers are generally substituted by cardinal numbers, as --

La página veintidós: Page 22nd.

Dates are expressed by cardinal numbers instead of ordinal, as --

Madrid, 20 (de) Agosto (de) 1911: Madrid, 20th of August, 1911.

EXCEPTION: El primero, as --

El 1° (primero) de Septiembre (1st September).

Numbers following names of kings, etc., are ordinal up to the tenth; then generally cardinal, as --

Felipe II. (segundo): Philip II.
Alfonso XIII. (trece): Alphonso XIII.

Fractional numbers up to 1/10th are the same as ordinal numbers, except --

(Un) medio: one half.
Un tercio (not tercero): one-third.

From 1/11th upwards, fractions are formed from cardinal numbers adding to them the termination avo, as --

Un dieciseisavo[65]: 1/16.

Un need not be used before the fractions 1/2, 1/3 and 1/4, preceded by an integer, as --

Uno y cuarto: One and a quarter.
Cuatro y tercio: Four and a third.
La mitad: The half.
La tercera parte: The 3rd part.
La cuarta parte: The 4th part.
La duodécima parte: The 12th part.

Footnote 65: If the cardinal number ends in a vowel, this is elided, as veinte -- un veintavo (1/20th). If it ends in ce the c is changed into z as, doce -- un dozavo (1/12th).

Collective Numbers.

 Un par: A pair.                 Una treintena: A set of 30.[66]
 Una decena (half a score).[66]  Una centena: A set of 100.[66]
 Una docena (a dozen).[66]       Un centenar: A set of 100.[66]
 Una veintena: A score.[66]      Un ciento: A set of 100.[66]
                                 Un millar: A set of 1,000.[66]

Footnote 66: Also the number approximately, as: Una treintena de libros: (about 30 books).

Subjunctive Mood,[67] Present Tense.

 Hablar.              Temer.                Partir.

 Que yo hable (That I    Que tema (that I may    Que parta (that I may
  may or shall            or shall fear).         or shall depart).
  speak).
  "  tu hables            "  temas                "  partas
  "  él hable             "  tema                 "  parta
  "  nosotros hablemos    "  temamos              "  partamos
  "  vosotros habléis     "  temáis               "  partáis
  "  ellos hablen         "  teman                "  partan

Footnote 67: This tense is formed from the first person singular of the present indicative by changing the last vowel into e for the 1st conjugation and into a for the 2nd and 3rd conjugations. These remain the ruling vowels throughout the tense.

N.B. -- The Subjunctive Mood occurs only in dependent sentences when the action is not expressed in a positive manner but is doubtful or merely contingent.