Sometimes it’s convenient to render a phrase like saber of light or barroom sport of tossing dwarves as a single word like lightsaber or dwarf-tossing. Such words are called compound words.
Despite alleged monstrosities like Finnish lentokonesuihkuturbiinimoottoriapumekaanikkoaliupseerioppilas and German Schützengrabenvernichtungsautomobil, compounds are often shorthand renderings of even longer constructions in Ido, like harbrosilo (“hairbrush”) from harala brosilo or brosilo por hari.
Compound words generally consist of a head (a word that expresses the basic meaning of the whole compound) and one or more modifiers. (E.g., handbrake consists of the head brake, the basic meaning of the compound, and hand, describing the sort of brake it is.)
In English, the head usually comes last in a compound, but this varies from language to language — and often within the same language (e.g., English lockpick and pickpocket, Spanish chupacabra and fazferir). Ido uses the model of Greek and Latin derived international compounds, where the main element, if any, comes last (e.g., astronaut “star-sailor”, anthropophage “man-eater”).
|akradolcajo||[akra e dolca]-ajo||bittersweet thing|
|enklostrigar||[en klostro]-igar||to cloister|
|Kad ulu dicis « Tondrofurio, benedikita lamo di la ventoserchanto »?||[furio di tondro, serchanto di vento]||Did someone say “Thunderfury, Blessed Blade of the Windseeker”?|
There are some “exocentric” compounds that denote something other than a form of the head. For example, silverback denotes not a type of back, but a male ape characterized by a silver back, and before-tax denotes not a type of tax, but profits reckoned before taxes. Here, too, Ido follows the model of Greek and Latin international compounds (e.g., apathy “without-feeling”).
|superhomo||[(ulu) super homi]||superman|
|avanchambro||[(ulo) avan chambro]||ante-chamber|
Note that Ido elides the final vowel of the first element(s) in a compound where euphony allows, but otherwise retains it if it exists:
|laser-espadala||[espado ek lasero]-ala||pertaining to lightsabers|
|partoprenar||[prenar parto]||to partake|
|cielblua||[blua quale la cielo]||sky-blue|
|apudpozar||[pozar apud]||to juxtapose|
|subtaso||[(ulo) sub taso]||saucer|
|trianguli||[(uli kun) tri anguli]||triangles|
As compound words are abbreviations of longer, but often clearer phrases, one should take care not to overuse them — especially in speech, where some compounds in Ido are indistinguishable from non-compounds: subtaso / sub taso “saucer / under a cup”, trianguli / tri anguli “triangles / three angles”, aquoblua / aquo blua “aqua blue / blue water”, sabrofrapita / sabro frapita “saber-struck / a struck saber”.
When a preposition is combined with a verb that can take an object, the preposition is treated as an adverb with an elided -e and the object of the compound is the object of the original verb:
|deprenar chapelo||[de-e prenar chapelo]||to take off a hat|
When a preposition is combined with a verb of motion that does not take an object, the object of the preposition can be used as the object of the compound to signify motion toward that object:
|advenar (ad) konkordo||[venar ad konkordo]||to come to an agreement|
|enirar chambro||[irar aden chambro]||to enter a room|