Greek Military: Units of Measurement

Different types of units were divided differently and therefore their leaders had different titles. For example, under a numbering system by tens, a dekas or dekania was a unit of ten led by a dekarchos, a hekatontarchia was a unit of hundred led by a hekatontarchos and a khiliostys or khiliarchia was a unit of a thousand led by a khiliarchos.

Source: Wikipedia