Esperanto is a planned (constructed) international auxiliary language. The name derives from the pseudonym (Dr. Esperanto) under which L. L. Zamenhof published the language in 1887. (See Esperanto history.) His intention was to create an easy-to-learn language, to serve as an international auxiliary language for global communication. Today Esperanto is used for many activities including travel, correspondence, cultural exchange, literature, and language instruction; it is the most widely used constructed auxiliary language.
A declaration endorsed by the Esperanto movement in 1905 limits changes to the Esperanto principle. That declaration stated, amongst other things, that the basis of the language should remain Fundamento de Esperanto ("Foundation of Esperanto", a work by Zamenhof), which is to be binding forever: nobody has the right to make changes to it. The declaration also permits new concepts to be expressed as the speaker sees fit, but it recommends doing so in accordance with the original style.
Esperantists believe Zamenhof's approach is why Esperanto is uniquely strong among constructed languages. More generally, there are five primary reasons for its strength:
However, modern Esperanto usage may in fact depart from that originally described in the Fundamento. The translation given for "I like this one", in the phrases below offers a significant example. According to the Fundamento, Mi ŝatas ĉi tiun would in fact have meant "I esteem this one". The traditional usage would instead have been Ĉi tiu plaĉas al mi (literally, "this one is pleasing to me"), which, although it differs from the English phrasing in "I like this one", more closely reflects the phrasing in several other languages (e.g. French celui-ci me plaît, Spanish éste me gusta, Russian это мне нравится [eto mnye nravitsya], German Dieses gefällt mir).
Other changes from traditional Esperanto have affected the names of countries, whose endings have changed from -ujo to -io. Also, women's names ending in -a (e.g. Maria) are now recognized although this is strictly an adjectival ending, whereas previously purists would have insisted on the noun ending -o (e.g. Mario).
In addition to these, Esperantists have formed many words to express concepts which have arisen more recently, but where possible these have indeed conformed to the existing style of the language. For example, "computer" is komputilo, (adding the suffix -il- meaning a tool to the root of the verb komputi, 'to compute'). Eŭro (as in these phrases) is another good example: even though the currency is called euro in all the European Community's official languages which use a Latin script, in Esperanto Eŭro was chosen because it better fits the phonology of the language.
An estimate of the number of Esperanto speakers was made by Sidney S. Culbert, a retired psychology professor of the University of Washington (himself a longtime Esperantist who commented regarding the logical structure of Esperanto: "If the world could be structured that efficiently"). Culbert concluded that 1.6 million people speak Esperanto at Foreign Service Level 3, limited to those "professionally proficient" (possessing the ability to actually communicate beyond greetings and simple phrases). Culbert's estimate was not made for Esperanto alone, but formed part of his listing of estimates for all languages of over 1 million speakers, published annually in the World Almanac and Book of Facts. In the Almanac, his estimates for numbers of language speakers were rounded to the nearest million, thus the number for Esperanto speakers is shown as 2 million. This latter figure appears in Ethnologue. Assuming that this figure is accurate, this means that about 0.03% of the world's population speaks the language. Although this falls short of Zamenhof's goal of a universal language, it must be remembered that this level of popularity is unmatched by any other constructed language. Ethnologue also states that there are 200 to 2000 native Esperanto speakers.
Ethnologue also states that Esperanto is a language of France  (http://www.ethnologue.com/show_language.asp?code=ESP). David Blunkett said in the House of Commons: "My only regret is that I learned a language called Esperanto at school. It was a very good idea at the time, but it got me into certain difficulties at the age of 16 when I used it in Paris."  (http://www.publications.parliament.uk/pa/cm200001/cmhansrd/vo010426/debtext/10426-03.htm), although he did not say whether he had been reading Ethnologue.
Ziko Marcus Sikosek has challenged this figure as exaggerated. Sikosek estimated (in Esperanto Sen Mitoj -- "Esperanto without Myths") that even if Esperanto speakers were evenly distributed (in fact, they seem to be more numerous in Europe and east Asia than in other regions, and more numerous in cities than in rural areas), assuming one million Esperanto speakers worldwide would lead one to expect about 180 in the city of Cologne. Sikosek finds only 30 fluent speakers in that city, and similarly smaller than expected figures in several other places thought to have a larger than average concentration of Esperanto speakers. He also notes that there are a total of about 20,000 members of the various Esperanto organizations, and (though there are undoubtedly many Esperanto speakers who are not members of any Esperanto organization) thinks it unlikely there are as many as 50 times more speakers than organization members, although he provides no scientific basis for this assumption.
Esperanto is not an official language of any country, although there were plans at the beginning of the 20th century to establish Neutral Moresnet as the world's first Esperanto state, and the shortlived artificial island micronation of Rose Island used Esperanto as its official language in 1968. However, it is the official working language of several non-profit organizations, mostly Esperanto organizations.
Goals of the Esperanto Movement
Zamenhof's intention was to create an easy-to-learn language, to serve as an international auxiliary language, a second language for everyone in the world, rather than to replace all existing languages in the world. Some Esperanto speakers, or Esperantists, still want this (they are called finvenkistoj -- from fina venko meaning "final victory"), but others just want to use the language to meet foreigners and learn about other countries and cultures (called raŭmistoj -- from Rauma in Finland, where a declaration was made to that effect).
Dialects and derived languages
No new languages or dialects have formed through fragmentation of Esperanto as they do in natural languages, due mainly to the regular nature of the language and its intended field of use. People tend to create slang and regional variants in the language(s) they use day to day, rather than those used primarily for intercommunication with different-language speakers; in the case of Esperanto, such variations, if heavily different from the official Fundamento version, would make universal comprehension less likely and negate the intended purpose of the language.
Esperanto has slang words - for example, saluton (hello) is sometimes clipped to sal and fajfi (to whistle) is often used to mean not to care about something. There are many other slang and swear words. There is not as much slang in Esperanto as in other languages, because slang tends to make international communication more difficult.
Through the years many groups and individuals have proposed new language projects as 'reformed' versions of the Esperanto. Almost all of these projects have remained stillborn, failing to progress past the planning stage, and the only ones to have had an amount of success have been Interlingua and Ido (Esperanto for 'offspring'). Ido was proposed by the Delegation for the Adoption of an International Auxiliary Language in Paris in October 1907. Its main differences were in the fields of alphabet and some grammatical features. Early on there was a relatively large number of people who moved their support behind the Ido project, but the movement itself descended into fragmentation and decline as others proposed further changes. Modern estimates place current speakers of Ido between 250 and 5000.
Some small-scale reform projects, affecting only a small part of the language, have gained a few adherents speaking a somewhat idiosyncratic version of the language: for instance, Riismo, the use of an epicene third-person pronoun "ri" in place of the masculine and feminine "li" and "ŝi" and a suffix -iĉ (parallel to -in) to form masculine terms from gender-neutral roots (e.g. frato = brother or sister, fratiĉo = brother, fratino = sister).
Esperanto is written using a modified version of the Latin alphabet, with six accented letters: ĉ, ĝ, ĥ, ĵ, ŝ (c, g, h, j, and s with circumflex), and ŭ (u with breve). The alphabet does not include the letters q, w, x, and y.
The unaccented letters are pronounced as the lower-case equivalents in X-SAMPA, with the exception of c, which is pronounced [ts]. ĉ is pronounced [tS]. ĝ is pronounced [dZ]. ĥ is pronounced [x]. ĵ is pronounced [Z]. ŝ is pronounced [S]. ŭ is pronounced [U], and normally follows an a, e or o; it never appears at the beginning of a syllable except in onomatopoeia. Diphthongs can be formed by the letters j and ŭ.
(See the external PDF file The Alphabets of Europe (http://www.evertype.com/alphabets/esperanto.pdf).)
The six Esperanto accented characters are included in the international form of Morse code.
Additionally, Esperanto can also be written using 'cx', 'gx', 'hx', 'jx', 'sx', and 'ux' instead of the 6 special characters ĉ, ĝ, ĥ, ĵ, ŝ, and ŭ. This is mainly used on computers or typewriters where typing the 6 special characters is impossible or inconvenient.
Formerly most Esperanto texts, if they used the circumflexed letters at all, were encoded with ISO 8859-3. Support for that codepage was not widespread. Today everybody seems to have switched to Unicode.
Most operating systems have no built-in keyboard layouts for Esperanto, so typing Esperanto texts requires some additional tools.
Also, the proper computer support for Esperanto requires a locale definition. Possible recommendation for locale is as follows: "." as the thousands separator and "," as a decimal point; 24-hour time with colon between hour and minutes; for dates use a four-digit year and write out the month name or abbreviation thereof.
Some studies suggest that Esperanto is a good deal easier for speakers of European languages to learn as a second language than any natural language (especially languages such as English, French, and Chinese).
There is also some evidence that suggests studying Esperanto before studying any other second language (especially an Indo-European language) may speed and improve learning, because learning subsequent foreign languages is easier than learning one's first, while the use of a grammatically simple auxiliary language lessens the "first foreign language" learning hurdle. In one study (Williams 1965), a group of high school students studied Esperanto for one year, then French for three years, and ended up with a better command of French than the control group, who studied French without Esperanto during all four years. However, the study failed to prove that Esperanto was responsible for this advantage specifically, as it is likely that learning any language will benefit the future study of other languages.
Today, people often learn Esperanto online through websites like lernu!
Here are some examples of Esperanto sentences, with rough pronunciation guides. The five vowels ought to have roughly the same qualities that they do in Italian, Spanish, Tagalog, Maori, Swahili, and many other languages, as well as in the International Phonetic Alphabet. They are all pure vowel sounds (avoid making a dipthong - particularly of the "o"), and are of medium length - so neither clipped, nor drawn-out.
The stress syllable in Esperanto words is always the last but one - shown capitalized in the examples here:
Information on Esperanto