L'hémisphère ouest est la moitié de la Terre qui est comprise à l'ouest du méridien de Greenwich jusqu'au 180e méridien.
Il couvre pour l'essentiel l'ensemble du continent américain, l'ensemble de l'océan Atlantique et une grande partie de l'océan Pacifique. En complément, il couvre les parties occidentales extrêmes du continent européen et du continent africain ainsi qu'une partie de l'Antarctique.
Les longitudes y sont inscrites soit par des nombres négatifs soit par la mention « Ouest ». Par exemple : « -65° » ou « 65° O ».
Nukutavake or Nukutuvake is an island in the Tuamotu group in French Polynesia. It lies 1,125 km from Tahiti. The closest land is small Pinaki Atoll, located 15 km to the southeast. Vairaatea Atoll lies 38 km to the west of Nukutavake.
Nukutavake's length is 5 km and its width between 0.45 and 1.3 km. Nukutuvake is not a typical Tuamotu atoll, but a single island. It was formed when its lagoon filled up with silt, in a similar manner as Fua Mulaku in the Maldives, which has a similar size and shape. There are shallow remains of the lagoon filled with marshy vegetation. The higher ground has many coconut palms.
Nukutavake has 139 inhabitants; Tavananui is the largest town. Many islanders have left the island in recent years, mainly to Tahiti, in search for work. There are a number of abandoned houses on the island. The people who remain live primarily on fish and copra production. There is a cyclone shelter on Nukutavake