A spell is words uttered in a set formula with magical intent. The correct recitation, often with accompanying gestures, is considered to unleash supernatural power. Some societies believe that incorrect recitation can not only nullify the magic but cause the death of the practitioner. The language of spells is sometimes archaic and is not always understood by the reciter. In some cases meaningless but familiar terms are believed to be efficacious because of their traditional value. Much magical language, however, is clearly and directly correlated with the aim of the recital. In symbolic statement by analogy it represents and foreshadows the technical achievement, and metaphor and simile are freely used. An example is a Maori spell giving speed and grace to a canoe, which speaks of the swiftness of a bird on the wing and the lightness of a sea gull and which uses such onomatopoeic effects as speed noises or the wailing of the sea. In blessings and curses, which are similar types of verbal expressions, the efficacy of the recitation is also believed to be connected to the magical power of the words themselves or to the sacred power of a supernatural being. Certain gestures as well as words may be bound up with the act of blessing, as in putting one's hands on the head of the person being blessed. The curse, a wish to cause harm or misfortune, is usually directed against others, although an important form of curse, associated with oaths, contracts, and treaties, is conditionally directed against oneself, should one fail to keep one's word or tell the truth.