Haka (ˈhɑːkə; singular haka, in both Māori and English) are a variety of ceremonial dances in Māori culture. Haka are often performed by a group, with vigorous movements and stamping of the feet with rhythmically shouted accompaniment. Haka have been traditionally performed—by both men and women—for a variety of social functions within Māori culture. They are performed to welcome distinguished guests, or to acknowledge great achievements, occasions, or funerals. Kapa haka groups are common in schools. The main Māori performing arts competition, Te Matatini, takes place every two years. New Zealand sports teams' practice of performing a haka to challenge opponents before international matches has made the dance form more widely known around the world. This tradition began with the 1888–89 New Zealand Native football team tour and has been carried on by the New Zealand rugby union team (known as the All Blacks) since 1905. Although popularly associated with the traditional battle preparations of male warriors, conceptions that haka are generally war dances, and the non-accurate performance of haka by non-Māori, are considered erroneous and sometimes offensive by Māori scholars. The group of people performing a haka is referred to as a kapa haka (kapa meaning group or team, and also rank or row). The Māori word haka has cognates in other Polynesian languages, for example: Samoan saʻa (saʻasaʻa), Tokelauan haka, Rarotongan ʻaka, Hawaiian haʻa, Marquesan haka, meaning 'to be short-legged' or 'dance'; all from Proto-Polynesian saka, from Proto-Malayo-Polynesian sakaŋ, meaning 'bowlegged'. According to Māori scholar Tīmoti Kāretu, haka have been "erroneously defined by generations of uninformed as 'war dances, while Māori mythology places haka as a dance "about the celebration of life". Following a creation story, the sun god, Tama-nui-te-rā, had two wives, the Summer Maid, Hine-raumati, and the Winter Maid, Hine-takurua. Haka originated in the coming of Hine-raumati, whose presence on still, hot days was revealed in a quivering appearance in the air.