(_g_). Unu is sometimes used when our indefinite article is employed as a numeral.[14]
Example.--_Ĉar ĉiu el ni havas unu vortaron, prenu vian kaj lasu mian_ = Since we have each _a_ dictionary, take yours and leave mine.
[14] This use of _unu_ is not recommended.
116. Ordinal numbers, being really adjectives, are, in Esperanto, made such in the usual way by adding _A_ to the cardinals, as:--unua = _first_, dua = _second_, tria = _third_, kvara = _fourth_, kvina = _fifth_, sesa = _sixth_, sepa = _seventh_, oka = _eighth_, naŭa = _ninth_, deka = _tenth_.
(_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_.