Volapük is a constructed language. Its ISO 639 language codes are vo and vol.
Volapük was created in 1879-1880 by Johann Martin Schleyer, a Catholic priest in Baden, Germany. Schleyer felt that God had told him in a dream to create an international language. Volapük conventions took place in 1884 (Friedrichshafen), 1887 (Munich), and 1889 (Paris). The first two conventions used German, and the last conference used only Volapük. As of 1889, there were an estimated 283 clubs, 25 periodicals in or about Volapük, and 316 textbooks in 25 languages.
Schleyer adapted the vocabulary mostly from English, with a smattering of German and French, and often modified it beyond easy recognizability. For instance, "vol" and "pük" are derived from the English words "world" and "speak". Polysyllabic words are always stressed on the final syllable, regardless of how the source language places the stress. Although unimportant linguistically, and regardless of the simplicity and consistency of the stress rule, these deformations were greatly mocked by the language's detractors. It seems to have been Schleyer's intention, however, to deform its loan words in such a way that they would be hard to recognise and thus lose their ties to the language(s) - and, by extension, nations - they came from. Compare the common criticism that Esperanto (and to a greater degree Interlingua) is much easier to learn for Europeans than for those with non-European native languages.
The grammar is roughly based on that of Indo-European languages but with a regularized agglutinative character: grammatical features are indicated by putting together unchanging elements, rather than shifting, multi-meaning inflections.
As in German, the Volapük noun has four cases: nominative, genitive, dative, and accusative. In compound words, the first part of the compound is usually separated from the second by the genitive termination "-a", e.g. Vola-pük, "of-world language". However, the other case endings (-e dative, -i accusative) are sometimes used, or the roots may be agglutinated in the nominative, with no separating vowel.
Adjectives, formed by the suffix "-ik", normally follow the noun they modify. They do not agree with the noun in number and case unless they precede the noun or stand alone. Adverbs are formed by suffixing "-o" to the adjectival "-ik"; they normally follow the verb or adjective they modify.
The verb carries a fine degree of detail, with morphemes marking tense, aspect, voice, person, number, and (in the third person) the subject's gender. However, many of these categories are optional, and a verb can stand in an unmarked state. (It has been claimed that the full conjugation of a verb in Volapük can involve 500,000 forms.)
Not only verbs, adjectives and adverbs, but prepositions, conjunctions and interjections can be formed from noun roots by appending appropriate suffixes.
Earlier versions of Volapük added vowels from blackletter typefaces to the antiqua ones. Later versions replaced them with the Roman vowels with diaereses added.
Schleyer first published a sketch of Volapük in May 1879 in Sionsharfe, a Catholic magazine of which he was editor. This was followed in 1880 by a full-length book in German. Schleyer himself did not write books on Volapük in other languages, but other authors soon did.
The Flemish cryptographer Dr. Auguste Kerckhoffs was for a number of years Director of the Academy of Volapük, and introduced the movement to several countries. However tensions arose between Dr. Kerckhoffs and others in the Academy, who wanted reforms in the language, and Schleyer, who insisted strongly on retaining his proprietary rights. This led to schism, with much of the Academy abandoning Schleyer's Volapük in favor of Idiom Neutral and other new constructed language projects. Another reason for the decline of Volapük may have been the rise of Esperanto. In 1887, the first Esperanto book (Unua Libro) was published. As the language was easier to learn, many Volapük clubs became Esperanto clubs.
In the 1920s Arie de Jong, with the consent of the leaders of the small remnant of Volapük speakers, made a revision of Volapük which was published in 1931. This revision was accepted by the few speakers of the language. de Jong simplified the grammar, eliminating some rarely-used verb forms, and eliminated some perceived sexism in the pronouns and gendered verb endings. He also added the phoneme "r" and used it to make some morphemes more recognizable. For instance, "lömib" (rain) became "rein".
Volapük enjoyed a brief renewal of popularity in the Netherlands and Germany under de Jong's leadership, but was suppressed (along with Esperanto and other constructed languages) in countries under Nazi rule and never recovered.
There are an estimated 25-30 Volapük speakers in the world today.
Large Volapük collections are held by the International Esperanto Museum in Vienna, Austria; the Centre de documentation et d'étude sur la langue internationale in La Chaux-de-Fonds, Switzerland; and the American Philosophical Society in Philadelphia, Pennsylvania. 
The Lord's Prayer
O Fat obas, kel binol in süls, paisaludomöz nem ola! Kömomöd monargän ola! Jenomöz vil olik, äs in sül, i su tal! Bodi obsik vädeliki govolös obes adelo! E pardolös obes debis obsik, äs id obs aipardobs debeles obas. E no obis nindukolös in tendadi; sod aidalivolös obis de bas. Jenosöd!
Ven lärnoy püki votik, vödastok plösenon fikulis. Mutoy ai dönu sukön vödis nesevädik, e seko nited paperon. In dil donatida, ye, säkäd at pebemaston, bi tradut tefik vöda alik pubon dis vöds Volapükik. Välot reidedas sökon, e pamobos, das vöds Volapükik pareidons laodiko. Gramat e stabavöds ya pedunons in nüdug; too loged viföfik traduta pakomandos ad garanön, das sinif valodik pegeton. Binos prinsip sagatik, kel sagon, das stud nemödik a del binos gudikum, ka stud mödik süpo.
When one is learning another language, vocabulary presents difficulties. One must continually search for unknown words, and consequently interest is lost. In the elementary part, however, this problem has been overcome, because the relevant translation of each word appears below the Volapük words. A selection of readings follows, and it is suggested that the Volapük words are read out loud. The grammar and a basic vocabulary have already been done in the introduction; nevertheless, a quick glance at the translation is recommended to ensure that the overall meaning has been acquired. It is a wise maxim which states that a little study a day is better than a lot of study all at once.
Schleyer, Johann Martin, Sigmaringen, 1879-1880.
Langue à racines naturelles déformées. Dérivation arbitraire, schématique formant des familles régulières de mots. Fixité des parties du discours, sauf du substantif.
- Vükiped, The Volapük Wikipedia
- Handbook of Volapük, Charles E. Sprague (1888)
- A ten-lesson course in modern Volapük
- Volapük links page
- "Arie de Jong's Revision of Volapük (1931)" by Ed Robertson. From the 21st edition of the Journal of Planned Languages, 1995.
- Article on Volapük from the 1911 Encyclopaedia Britannica
- Volapük bibliography
- Volapükalised - A Volapük group on Yahoo, general discussion in Volapük about any topic and about Volapük in various other languages
- Vödasbukalised - Volapük terminology group on Yahoo
- Glup ICQ Volapükik
- Blueprints for Babel: Volapük - A summary of the grammar of Volapük