Greek military ranks
In the army and air force, these names are often based on the unit or post that a holder of each rank usual commands. For example, a tagmatarchis is in charge of a tagma, which is derived from an Ancient Greek word translatable as "command", "order", or "class", and in modern Greek is a unit equivalent to a battalion in other armies; hence a modern tagmatarchis is a rank equivalent to major in other armies. Similarly, a lochagos normally commands a lochos (a word that originally meant "warband") , which in Ancient Greece was a 100-strong hoplite unit, but in modern Greek usage is equivalent to an infantry company. Hence a lochagos is the equivalent of a captain in other armies, and the modern Greek equivalent of an army first lieutenant is the modern neologism ypolochagos: literally, "sub-captain". Likewise, the modern Greek equivalent of a sergeant is a lochias.
The suffixes -agos and -archos (or -arches), which are often found in Greek rank names, are derived from the roots agein "to lead" and archein "to rule", respectively.