[Zen]

You know with all this talk of Tau not being of the normal government system that's common amongst other Empires, why don't call themselves the Federation of Tau'va or something. Also, I don't see a Tau Emperor that would be an obvious signs that it should be called Tau Empire.

[Doombringer]

I'd say the simplest answer is that it is called such, because Empires don't need to be ruled by an Emperor.

Empires are also commonly ruled by Oligarchies, which is what we have with the Tau...

Originally Posted by Empire - wikipedia

The term empire derives from the Latin imperium. Politically, an empire is a geographically extensive group of states and peoples (ethnic groups) united and ruled either by a monarch (emperor, empress) or an oligarchy.

Originally Posted by Oligarchy - wikipedia

An oligarchy (Greek ?????????, Oligarkhía) is a form of government in which power effectively rests with a small elite segment of society distinguished by royal, wealth, intellectual, family, military or religious hegemony.

Voila! The Tau Empire.

[khanaris]

They are also an Empire in the sense of the British Empire, where one culture is subjecting a number of others to its (theoretically benevolent) rule without providing complete representation.

[Fate13]

I would liken it more to the Roman empire historically, but that is just nit-picking on my part. In any case the other posters are correct in their explanations. While I like the sound of it, the Tau Empire is ruled by the Tau and hence their state's name must imply this, which federation of Tau'va does not.

[Watchdog]

I would like to offer another explanation.

The term "Tau Empire" comes from the Imperial language. It is a rough translation of the original term used by the Tau. Which term that is I am unsure of though. Many of the Tau unit names (for instance Hammerhead, Sky Ray, Piranha, Devilfish...) are just Imperial military code designations of Tau vehicles, based on their appearance, since the original names are not known or maybe the translations, if at all possible would sound too dull or make no sense. The similar happened with NATO-Warsaw pact unit names. For instance, Mig-25 was codenamed "Foxbat" by NATO.

[trogdor16]

I think they should change it to United Socialist Tau Republic