Hawaii (/həˈwaɪ.i/ ⓘ hə-WY-ee;[9] Hawaiian: Hawaiʻi [həˈvɐjʔi, həˈwɐjʔi]) is an island state of the United States, in the Pacific Ocean about 2,000 miles (3,200 km) southwest of the U.S. mainland. It is the only state not on the North American mainland, the only state that is an archipelago, and the only state in the tropics. It also hosts 10 out of 14 climates - the highest for any country subdivision - and is one of two U.S. states with a tropical climate. Hawaii consists of 137 volcanic islands that comprise almost the entire Hawaiian archipelago (the exception, which is outside the state, is Midway Atoll). Spanning 1,500 miles (2,400 km), the state is physiographically and ethnologically part of the Polynesian subregion of Oceania.[10] Hawaii's ocean coastline is consequently the fourth-longest in the U.S., at about 750 miles (1,210 km).[d] The eight main islands, from northwest to southeast, are Niʻihau, Kauaʻi, Oʻahu, Molokaʻi, Lānaʻi, Kahoʻolawe, Maui, and Hawaiʻi, after which the state is named; the latter is often called the "Big Island" or "Hawaii Island" to avoid confusion with the state or archipelago. The uninhabited Northwestern Hawaiian Islands make up most of the Papahānaumokuākea Marine National Monument, the largest protected area in the U.S. and the fourth-largest in the world.