Etymologically, it is derived from the roots *μερ- and *μορ-, which mean "to part".
Moira therefore means "a part, a division", and is cognate with the similar term meros.
In the Byzantine period, it was used to denote brigade or division-sized commands, while in the modern Greek military, it is used by some branches to designate battalion-sized units.
In the late 6th to early 7th century, the Late Roman military system, which was still in use by the East Roman or Byzantine Empire, went through a process of martial transformations that culminated with the establishment of the new military-administrative theme system in the 680s.
[1] In the Hellenic Air Force, but also in the Aviation services of both Army and Navy, moira (Greek: μοίρα, plural μοίρες) is the term used for squadrons.