A noun is any sort of person, place, or thing, and comes in two varieties: common and proper.
Common nouns are generic words that identify members of a class of people, places, or things. In Ido, all common nouns end in -o:
The plural changes the final -o to -i:
Words that are not already nouns can be made into one simply by adding -o to the root:
|maligno (from maligna “malignant”)||evil person or thing|
|sorco (from sorcar “bewitch”)||incantation|
|extero (from exter “outside of”)||outsider|
The -o of Ido nouns should not be confused with the masculine -o of Spanish and Italian; every noun in Ido, whether it’s male, female, neuter, or epicene, ends in -o. So to specify that a noun is male or female, one can add -ul- or -in- to the root:
Note that -ul- and -in- should only be used to avoid potential confusion. When speaking about gesiori Smith (“Mr. and Mrs. Smith”, the prefix ge- specifying both Mr. and Mrs. together), for example, one might need to distinguish between siorulo Smith (“Mr. Smith”) and siorino Smith (“Mrs. Smith”), but not when addressing either one of them directly (both are Sioro Smith).
Proper nouns name a particular person, place, or thing, and as such have no generic ending; they are treated as immutable “foreign” loanwords, pronounced as closely as one can get to the original within the limits of the Ido phonetic system. Those originally written in the Roman alphabet are transcribed as-is; those written in other alphabets are transcribed phonetically. Such words include names of individual people as well as words that are exclusively national or local:
|Wałęsa (o Walesa)||Wałęsa|
|Sheol||Sheol / שְׁאוֹל|
|samurai||samurai / 侍|
|Beijing||Běijīng / 北京|
|München (o Munchen)||München|
To form the plural of foreign words, one can use the native form if one knows it, or simply add -i (including the hyphen) where necessary: Noldor/Noldo-i, Weltschmerzen/Weltschmerz-i.
Unlike other “foreign” words, biblical and Christian given names do undergo some Ido-izing in that ch and hard c are transcribed k and ph is transcribed f — but otherwise adhere to their Latin or Latinized forms of the nominative case:
|Iakobus||Jacob, Giacomo, Jaques, etc.|
|Adolfus||Adolf, Adolph, Adolfo, etc.|
|Rafael||Raphael, Rafaelo, Rafaele, etc.|
|Ioannes||John, Johann, Jean, Giovanni, Ivan, etc.|
|Zakarias||Zachariah, Zachary, Zacarías, Zacharie, etc.|
|Ludovikus||Ludwig, Louis, Luigi, Hludwig, etc.|
The rules of Ido-izing such names are not consistent, however — sometimes something other than the Latin nominative case is used, sometimes the Latin termination is left off, sometimes intervocalic s is transcribed s, sometimes z:
|Iesu||IÉSV́S / ישוע|
|Isaias||ÍSÁIÁS / יְשַׁעְיָהוּ|
|Iozef||IÓSÉPHVS / יוֹסֵף|
The names of countries, oceans, and international rivers and mountain ranges preserve their Latin (or Latinized) form, but are more aggressively Ido-ized in their orthography and regularization:
|Usa*||The United States|
|Mediteraneo||The Mediterranean Sea|
|Pacifiko||The Pacific Ocean|
|Balkani||The Balkan Mountains|
In English, the name of a country’s inhabitants is sometimes the basis for the name of the country and language (e.g., “England” and “English” from the ancient Ængle), sometimes the other way around (e.g. “Congolese” from “Congo”). In the latter case, the language might instead be derived from the ethnic group whose language it is (“Spanish” in the case of Mexico), or have its own name (“Swahili” in the case of Kenya).
Theoretically, Ido simplifies this by deriving the names of all inhabitants from the country’s name by adding -an- to the root: an English person is an Angliano and speaks la Angliana, a Congolese is a Kongano and speaks la Kongana. Of course, this regularity is not always possible: a Mexikiano doesn’t speak la Mexikiana, but la Hispaniana, and a Keniano speaks la Swahilia.
In practice, however, Ido follows the model used by English and other languages and prefers, where applicable, the names of the ancient tribes after which their countries are named — even at the expense of Ido’s principle of reversibility. An English person, therefore, is an Anglo and speaks la Angla, a Spaniard is a Hispano and speaks la Hispana, a Belgian is a Belgo and speaks la Belga:
|Franco||a French person|
|la Franca||French (language)|
|la Portugaliana||Portuguese (language)|