The various human cultures on Euphrosyne speak English, but with noticeably different accents.
Mechanics
Mechanics have the most distinct accent. Their speech is hard to understand for most other inhabitants and vice versa. Because of this, most people can immediately tell someone is a Mechanic simply by their strong accent.
Clansfolk
Clansfolk also have a significant accent.
Remnant and Scavengers
Remnant and Scavengers mostly retain similar speech.
Nomads
Nomad speech heavily varies depending on the specific nomadic group.
Starborn
Another thing to note is that Starborn also have very distinct speech. To most Euphrosynians, they often sound very alien and somewhat retro. However, that heavily depends on their origin.
Tsiktral spawns
Spawns use a complex native language consisting of hisses and clicks. Some of these clicks exist at higher frequencies that are inaudible to humans. This language is impossible for humans or machines to decode or translate because it functions like a rapidly mutating biological cipher. The fundamental structure of the language shifts constantly; even if humans manage to understand it one day, it will be completely incomprehensible the next.
For an isolated spawn to understand its broodmates again, it must physically link its neuron connector to a spawn that possesses the most recent iteration of the language, or to an active Tsiktral root, and absorb the current linguistic structure.
While many smaller spawns are unintelligent, the larger castes are highly intelligent and often capable of speaking perfect English, though sometimes with an odd, hissing, clicking accent.