Galactic Basic Standard

Galactic Basic Standard (or Galactic Basic, Galactic Standard, Galaxy Standard or just Basic) was the most prevalent and most used language in the galaxy.

Evolution
Old Galactic Standard started as a slang or jargon of traders and spacers, based on a mix of early Human languages, Durese, and Bothese. Because of its popularity with members of those professions its popularity and acceptance spread. Old Galactic Standard was later further influenced by Dromnyr, resulting ultimately in the standard Basic.

Under the Galactic Empire, a version of the language was known as Imperial Basic. The language was adopted by the Rebel Alliance, and as such was spoken in the Alliance of Free Planets, the New Republic, the Imperial Remnant, the Galactic Alliance, and the Fel, Sith and True Empires.

Usage
Most sentient species that made galactic contact could and did speak Basic in addition to whatever native or regional language they might have used on a daily basis. Some beings normally did not possess the organs necessary to speak Basic, including Polis Massans, Ssi-Ruuk, P'w'ecks, Wookiees, and a number of insectoid races. Most Gamorreans could not speak Basic, though there were exceptions (such as Governor Kugg.) Whether or not a being could speak Basic, it was usually in their best interest to comprehend it, and most did.

The Towanis taught the Ewoks a mysterious and undocumented language, which didn't help them understand Leia Organa, and later, Han Solo and Luke Skywalker, who spoke Basic. The relation of that language to Basic is not known.

High Galactic was a dialect (perhaps a vocabulary of alternative words) intended for displaying reverence and honor to religious figures.

Basic used the Aurebesh script.

Known accents and dialects
Various cultures created different accents around the galaxy, each with their own unique set of pronunciations.
 * Barabel accent&mdash;as exemplified by Saba Sebatyne.
 * Cathar accent&mdash;as exemplified by Juhani.
 * Corellian accent&mdash;exemplified by Han Solo and Wedge Antilles. It was distinct enough so that a Corellian could instantly recognize another Corellian's speech.
 * Concord Dawn inflection&mdash;as exemplified by members of the Fett family. This was the most common accent among Mandalorians (perhaps due to the influence of their native language, Mando'a), with the tendency to pronounce words that had an 'e' with an 'i', e.g. word - delta, pronounced - dilta.
 * Coruscanti accent&mdash;as exemplified by Obi-Wan Kenobi, Palpatine, and Dooku. Most inhabitants of the Core Worlds, such as Mon Mothma, also spoke in this manner, whereas those from farther reaches did not, such as Padmé Amidala (Naboo), Luke Skywalker (Tatooine), and Leia Organa (Alderaan). In several instances, though, both Amidala and Organa spoke with a slight Coruscanti inflection when speaking to Nute Gunray and Wilhuff Tarkin respectively. It was suggested that this was their "court" voice to adopt an imperious air or bluff, since they lost this accent when in casual or stressed situations.
 * High Coruscanti&mdash;a more refined style of the Coruscanti accent. It was very posh and clipped and conveyed as sense of upper-class sensibility.
 * Eriaduan accent&mdash;as exemplified by Grand Moff Tarkin. It might have simply been an artifact of the heavy influence of Coruscant, or "standard" language throughout the Core Worlds, and by implication, the elite of society, since people in the Colonies and Outer Rim spoke differently.
 * Gungan dialect&mdash;as exemplified by Jar Jar Binks and Roos Tarpals.
 * High Galactic&mdash;An obscure dialect linked to religious figures.
 * Kaleesh accents&mdash;as exemplified by Grievous.
 * Neimoidian accent&mdash;exemplified by Nute Gunray and Rune Haako.
 * Yoda's dialect&mdash;an unusual form of Basic utilized by Jedi Grand Master Yoda and others of his tridactyl species, including Yaddle; it was characterized by an object-subject-verb format. However, another member of this species, Vandar Tokare, did not use this dialect.
 * Chiss accent&mdash;as exemplified by Baldarek on Nar Shaddaa.
 * Towani family dialect&mdash;this they taught to the Ewoks when they crashed on Endor. However it was not enough for those creatures to understand standard Basic a year later, when they met Princess Leia, Han Solo, Luke Skywalker, C-3PO, R2-D2 and the rest of the rebels.

Of interesting note, the Wookiee Ralrracheen spoke with a speech impediment. Due to the differences in the vocal abilities of Ralrra, his dialect was perfectly understandable by non Wookiees, and it was further suggested that some Wookiees with this condition could speak Basic, at the loss of all forms of Shyriiwook.

Basic-speaking Rodians tended to suffer from speech impediments as well, most notably a lisp. Avaro Sookcool and Teeloo were two such Rodians; the syllables R, L, and S proved to be the most problematic to vocalize.

Basic's relation to English
In both the films and books, Basic is, with the exception of some&mdash;still, English-based&mdash;words and phrases devised by authors, the same as English. This could mean two things: Either Galactic Basic actually is the same as the English language used today on Earth, or it is translated as English in a manner similar to Westron in J. R. R. Tolkien's Lord of the Rings. Languages of the Star Wars universe like Ewokese in the animated series and the language spoken by the Towanis in Caravan of Courage: An Ewok Adventure and Ewoks: The Battle for Endor have been translated to English in this manner.

In translations to non-English languages, Basic is assumed to be English but translated to the other language.

In E.T.: The Book of the Green Planet, a character mentions that she needs help with her "basic". However, in the context of the book, "basic" is most likely a reference to the computer programming language known by that name.

While the letters are different in Basic than English, there are multiple examples where latin alphabet letters are mentioned, such as Obi-Wan-Kenobi's quote "Do you have a plan B?", Misson Vao's habitual reference to Zaalbar as "Big Z", and most droid designations.

Accents
Dialects in English correspond to different in-universe accents in the movies. Ewan McGregor's and Ian McDiarmid's faint upper-class Scottish accents are, for example, Coruscanti accents in the movies. As a general rule, Imperial characters have English accents while Rebels usually have Californian accents. However, it would seem that this is perhaps a representation of social class, as stormtroopers and other low-ranking Imperials are heard to speak with American accents, and some Rebels in English accents (Mon Mothma, for instance). Other accents are also heard, such as:
 * Jamaican (Kit Fisto)
 * Irish (Emon Azzameen, Fenn Shysa, an unnamed Czerka officer outside Anchorhead in Star Wars: Knights of the Old Republic, Lurmen)
 * Scottish (Whorm Loathsom)
 * Japanese (Neimoidian)
 * New York/Brooklyn (the Chiss bartender Baldarek in Star Wars: Jedi Knight II: Jedi Outcast)
 * Australian (Owen and Beru Lars in Star Wars Episode II: Attack of the Clones as well as some Mandalorians in Star Wars: Knights of the Old Republic II: The Sith Lords)
 * New Zealander/Maori (The Fett family and clone troopers)
 * French (Aayla Secura)
 * Ukrainian (General Grievous) or Russian (Juhani and Queen Talia).
 * Swedish (Shmi Skywalker Lars)

Original etymology
Star Wars authors have coined original English-like words derived from real English elements but which don't exist in the English language; they seem useful to a space-driven civilization of the Star Wars characters, but totally useless for our daily language. Such words are 'speciesism' (equivalent to racism, but against sentient beings other than the speakers), 'gentlebeing' (equivalent to gentleman, but applicable to all species, including non-humanoid ones), 'offworlder', 'bird' (slang for spaceship, cf. how US Navy slang calls 'torpedo' as 'fish'), 'hyperspace', 'homeworld', 'spacer', 'sentientologist', 'youngling' (young + suffix -ling meaning 'person') and other technological terms like blaster, midi-chlorian, droid (from android), durasteel, astrogation etc.

However, Basic vocabulary includes some totally original, of unexplainable etymology, words also unrelated to English, like Moff, Jedi, Padawan, Darth etc. or even compounds like Twi'lek ("twin lekku"). It is possible that such words are derived from other languages.