(a). If the cardinal is composed of two or more numbers, A is added to the last only, as:—dek-unua = eleventh, dek-dua = twelfth, dek-naŭa = nineteenth, dudeka = twentieth, dudek-unua = twenty-first, cent-tridek-naŭa = hundred and thirty-ninth.
N.B.—Note that the ordinal numbers are linked by hyphens.
(b). The Ordinals follow all the rules of adjectives as to case and number.
Examples.—Donu al li la trian, kaj prenu la kvaran = Give him the third, and take the fourth. La kvinaj etaĝoj de tiuj domoj estas tre altaj = The fifth stories of those houses are very high.
(c). The Ordinals are usually used in speaking of pages, hours, days, months, years, kings, etc.
Examples.—Paĝo trideka = Page thirty. Vidu paĝon kvardekan (or, 40an) = See page forty (40). Henriko kvara = Henry IV. La dek-unua horo = 11 o’clock. En la dek-sesa (tago) de Aprilo = On the 16th of April. En la jaro mil-okcent-naŭdek-naŭa = In 1899. Mil-naŭcent-kvara = 1904.
In asking questions about the above, the adjective kioma is often used.
Examples.—Sur kioma paĝo vi vidis tion? = On what page did you see that? Kioma paĝo estas? = What page is it? Kioma horo estas? = What o’clock is it? Estas la dua = It is two o’clock. Kiun daton ni havas? = What is the date (or, day of the month)? Hodiaŭ estas la dudek-sepa (or, 27a) de Marto = To-day is the 27th of March.
117. Ordinal adverbs are formed by adding E to the cardinals, as:—unue, firstly, due, secondly, sepe, seventhly, etc.
118. Substantives are formed from the cardinals by adding O. They have various meanings, as:—Unuo = a unit, or a one. Duo = a duet, or a two (of cards). Trio = a trio, or triplet, or a three (of cards). Kvaro, etc. = a four, etc. (of cards, etc., up to ten). Dek-duo = a dozen. Deko = half a score. Dudeko = a score. Cento = a hundred. Milo = a thousand. Miliono = a million.