munth (chodhesh, yerach; men): Chodhesh is strictly the "new moon," the appearance of which marked the beginning of the month, commonly indicated by ro'sh ha-chodhesh. Yerach is derived from yareach, "moon," which comes from the verb that means "to wander," "to make a circuit." Thus the month was lunar, the period of the moon's circuit. The Greek men also meant "moon," from the Sanskrit ma, "to measure," the Latin mensis and our "moon" being derived from the same root.
Chodhesh, or rather ro'sh ha-chodhesh, was observed as a festival (1Sa 20:5,18,24; Isa 1:14).