Definition from Wiktionary, the free dictionary
Cardinal and ordinal numerals
- The number uno (“one”) apocopates (has its final sound or two removed) to un when used before masculine nouns or other numerals:
- The full form una is used with feminine nouns, unless the word begins with a stressed a- and cannot also exist as a masculine noun:
- The number ciento (“hundred”) apocopates to cien before all nouns and numbers greater than or equal to mil (“thousand”):
- el tercer edificio que he construido
- el primer buen conejo
- If a conjunction intervenes between the adjective and the noun, however, there is no shortening:
- un tercero y postrero golpe
- The use of a comma or dot to separate thousands varies throughout Latin America and Spain. The Real Academia Española accepts both.
- In writing, the numbers from 0 to 9 are usually written with words; the numbers above 20 are usually written as numerals.
- From 11 onward, ordinal numerals can be replaced with cardinal numerals to mean the same thing:
- decimoséptimo día, diecisiete día