There are a wide variety of languages in Charted Space. Most of them are known on only one planet, or in a small polity. A few are spread widely by the political and cultural influences of their speakers. The languages of this second group become widely known not as primary languages for a large number of planets, but as second languages for an entire region of space. The languages known as Trade Vilani, Galanglic, and Basic Sylean are languages that have served and do serve this purpose in Regency space.
Trade Vilani has its origins in the language now known as High Vilani. When the First Imperium was governing Imperial Space, the Vilani rulers, in an attempt to impose cultural homogeneity and stability on their empire, mandated the use of their language in all governmental and commercial communication. Since enforcement of this mandate was difficult at any level where the local populace was not dealing directly with Vilani, many people did not use Vilani in their day-to-day activities, and when they did need to use it, it was generally in a grammatically incorrect form that was nevertheless sufficient to transmit the intended meaning. In linguistics, these languages are called "pidgins".
It was economically impossible for the Vilani to maintain their absolute monopoly on the operation of starships once the size of the Imperium grew beyond the equivalent of six subsectors or so. This was still sufficient to ensure that some form of Vilani was in use on all of the planets as a "common" language. When planetary concerns and governments were permitted to operate their own starships, it was natural that they should use their ungrammatical Vilani to communicate with each other. There are examples from many planets demonstrating that communication has a leveling effect on dialectal differences; the First Imperium was proof that this same principle operated on an interstellar level as well. The result was "Trade Vilani".
The Rule of Man had a similar effect. Here, the mandated language was Terran Anglic, a language that was itself a pidgin (based on English) resulting from a commercial and technological advantage possessed by North America at the time that global communication and commerce became practical for the majority of the population, instead of for just a few large corporations. Changes in political and economic dominance allowed Spanish and Chinese to influence the language, and at the time that the Rule of Man was proclaimed, Terran Anglic would have been incomprehensible to an American or Englishman of Terran Year CE2000.
Most planets in the First Imperium had been using Trade Vilani in interstellar commerce; it was to be expected that it would continue to be used to fill in gaps in the speaker's knowledge of Terran Anglic, despite being officially "banned" from official use. The short duration of the Rule of Man, only 400 years, was sufficient to expose most planets to some use of Terran Anglic (which was now being called Galactic Anglic, or Imperial Anglic). Small communities of ethnic Terrans (or of people who considered themselves ethnic Terrans, despite having never been on Terra) were to be found on most of the important worlds of the Empire, including Sylea and Vland, as resident administrators. These communities survived into the Long Night, preserving the use of Imperial Anglic on those worlds, and on many nearby worlds within their economic influence.
During the Dawn, when the Zhunatsu family and their companies created the Sylean Federation, they took the pragmatic view of the question of language. Instead of mandating that Sylean be used exclusively, they gave it and Imperial Anglic equal status. De jure equality does not mean de facto equality, and it was quickly noticed that the use of Sylean offered subtle political and economic benefits when dealing with Syleans. Nevertheless, Imperial Anglic was firmly entrenched, and remained widely used, absorbing terms from Sylean as it had from Trade Vilani centuries earlier.
The Sylean Federation offered a high degree of autonomy to its member planets. In doing so, it relinquished its ability to influence linguistic development to the degree possible for the Rule of Man or the Vilani Imperium before it. As a result of this lesser influence, and the early decision to recognize the use of Imperial Anglic in government and commerce, the Sylean language never achieved the level of importance that Imperial Anglic and Trade Vilani achieved.
The creation of Basic Sylean was an effort to remedy this problem. Developed by a team of Sylean linguists, it offered a simpler grammatical structure, paralleling that of Imperial Anglic (although the more complex Sylean grammar could be used), and a reduced vocabulary. Inflections were for the most part eliminated, as were irregular verbs. Basic Sylean enjoyed a period of popularity, but it was not able to completely displace Imperial Anglic anywhere.
By the time Cleon I declared the Third Imperium, Imperial Anglic had been heavily influenced by Basic Sylean, and would have been incomprehensible to Admiral Estigarriba (Emperor Hiroshi I of the Rule of Man), or to any Terran/Solomani of the period immediately prior to the Rule of Man. Basic Sylean and Trade Vilani were still used in areas where recent influence from their respective planets of origin was strong, but Imperial Anglic, now universally called Galactic Anglic, or Galanglic, was de facto the primary common language of the Third Imperium throughout its expansion, and into the Rebellion period.
In spite of this, Trade Vilani, Terran/Imperial Anglic, and Basic Sylean can all be found in the Regency, due both to patterns of settlement and to the Imperial policy of local autonomy. Galanglic, as the official language of the Regency government, is used and understood almost everywhere in the Spinward States. It provides a common language that binds us together in a single interstellar community, and it is also the primary language for intership and ship-to-shore communications.
A dialect of Terran Anglic or Imperial Anglic is used for local communications in the former Sword Worlds, and in the few remaining independent worlds operating under that name. An even older dialect, heavily influenced by teZhlodh (the original Daryen native language) has the status not of a pidgin, but of a creole, in the Daryen Confederation.
Many parts of Deneb sector use Trade Vilani; these worlds were heavily influenced by the Vilani in the early days of colonization, as prior to the sector gaining Administered Sector status, it was governed from Corridor or Vland sector. Trade Vilani and Basic Sylean are used fairly heavily near the Aslan worlds in Trojan Reach sector; this is due to historical reasons in connection with contact with the Aslan: The original contact between the Imperium and the Aslan was in Daibei Sector, which was colonized by the Vilani during the First Imperium, and which maintained its Vilani-derived culture right through the Rule of Man and the founding of the Third Imperium and into First Contact with the Aslan. A dialect of Trade Vilani, heavily influenced by Trokh (and called by the Aslan trokh fiyalr) was thereby established as a trade language between the Aslan and the Imperium. When the Aslan were encountered on the other side of the Rift, the Sylean expedition that made contact was unable to communicate in trokh fiyalr, but since the commander of the Aslan fleet that made contact was the second son of a former Aslan ambassador to the Imperium, there was enough knowlege of Trade Vilani and Basic Sylean to establish communication. These languages became established for use in communicating with trans-Rift Aslan, as trokh fiyalr had in the rimward areas of the Imperium.