regio

Regio, regionis, f., third declension, off rego, "I rule, I direct, I draw straight". The first meaning is therefore a line drawn or a direction taken, and the territory is what happens to lie inside the line - the sense runs the opposite way round from English "region".

That older meaning survives in two places worth knowing. E regione, with a genitive or dative, means "straight opposite, facing". And the augurs divided the sky into regiones with an imaginary staff before reading the birds, which is the ritual ancestor of every later administrative district; Augustus split Rome itself into fourteen regiones. The root also gives rex, rectus, regnum, rego and regula, so region, rectitude, regulate and rule are all cousins.