The knowledge of the location of oases has been important for trade and transportation routes in desert areas. Caravans must travel via oases so that supplies of water and food can be refilled. Thus, political or military control of an oasis has in many cases meant control of trade on a particular route. For example, the oases of Awjila, Ghadames and Kufra, in modern-day Libya, have at various times been vital to both North-South and East-West trade in the Sahara desert. The word "oasis" came into English via Greek ����� , which was borrowed from Egyptian "wḥ3t" or Demotic "wḥỉ". It was not borrowed from Coptic "ouaḥe" (*/waħe/), as is sometimes suggested; the Greek word is attested several centuries before Coptic existed as a written language.