The Empire's language is Imperial Universum (from Schmidt). In my universe, this is descended from Terranic, which is descended from Earthron, which is descended from English. There are hundreds of local languages among Old Settlers and outside the Empire, but most Old Settlers and almost the entire general population of Imperial Space speaks Universum as a first or second language. Even on most non-Empire worlds, it is the first language.
Of course, accents and details of spelling and pronunciation vary from place to place. Sometimes "Imperial" Universum is reserved as the name for the dialect of Universum used by the educated classes and in the public media of the Empire.
Terranic differs from Universum mainly in using fewer Latin and Greek borrows. Universum-speakers can learn it easily, and passages in Terranic have a quaint flavor or an antique elegance for them. Terranic developed from Earthron by increasing the vocabulary borrowed from Conventional (a descendant of KaiSense) and Threenaleen. Its grammar has features borrowed from Conventional and Semantic. It is a language of literature. Many Old Settler languages are dialects or derivatives of Terranic.
Earthron is a pidgin developed from English, with a simplified grammar and many borrowings from Russian, Japanese, KaiSenese, and Threenaleen. It differs from Terranic in retaining the old Roman character set, in pronunciation, and in grammar. Earthron is uncouthly archaic to the ears of native Universum speakers.
Threenaleen is the racial language of the natives of Threenal, who have remarkable linguistic talent. It is a fantastically rich language, but with no immediate impact on the Reach. Universum borrows from it for place and species names.
KaiSenese and Conventional are artifical languages of interstellar, interspecies communication. Conventional is the revised version of KaiSenese introduced when the KaiSenese Association merged with the Trade Empire and Verity Household to unite the Ecumene in the Grand Convention. They supply some vocabulary (especially technical) and some grammatical features.
English, Latin, and Greek are languages of ancient learning, to the Reach. Latin and Greek supply vocabulary. English supplies the core vocabulary and basic grammar of Earthron, Terranic, and Universum.
As indicated, Universum speakers use Terranic to sound quaint or antiquely elegant. They use KaiSenese, English, Latin, and Greek for similar purposes, but the effect is more academic and learned, less romantic, to the Universan ear.
To sound "chic," Imperials use words and phrases from Riotamin or Jaidasic, both dialects of Universum heavily influenced by the local Old Settlers, both from culturally dynamic worlds outside the Empire.
To sound "cool," fashionably counter-cultural, Universum speakers use slang terms borrowed from the vocabularies of Old Settler languages, the favored languages changing with the fashions. Even more disreputably cool are Koliot words, borrowed from the language of the Raiders.
Koliot social slang in general use:
Koliot gambling & monetary slang in general use:
Koliot criminal slang in general use:
Koliot psi slang in general use:
Personal names in the general population follow the customs of the New Terraformers. People use a single given name and distinguish themselves, when necessary, by using the name of the same-sex parent as a second name. Thus Pausert, son of Mellus, is usually "Pausert" but sometimes "Pausert Mellus." Honorifics and titles are attached to the given name, not the parental name, so Pausert is "Captain Pausert," not "Captain Mellus."
Universum uses a wide variety of consonants, vowels, and diphthongs, but does not use consonant clusters much. When two consonants occur side by side, one of them (the one next to a vowel) is most often a nasal or liquid.
So st-, sk-, sp-, -bs, -st, and -fth rarely occur,
but bl-, pr-, sn-, -rt, -ngz, and -mp are allowed.
Universum uses a minor variation of the Roman alphabet, the Terranic, with the following additional letters:
With the novel letters bolded, the alphabetical order is, "Ay, be, shay, dee, edh, ee, ef, gee, aitch, aye, jay, kay, el, em, en, eng, oh, pee, hue, ar, ess, tee, thay, yew, vee, double-ay, double-oh, double-u, etch, wye, zee."
In addition to the Terranic alphabet, Universum uses a number of ligature symbols like the ampersand – ideograms for short, common words. Besides using & for "and," Universum also has symbols for "of," "to," "the," "an," and "is":
