The Benedictines, officially the Order of Saint Benedict (Latin: Ordo Sancti Benedicti, abbreviated as O.S.B. or OSB), are a mainly contemplative monastic order of the Catholic Church for men and for women who follow the Rule of Saint Benedict. Initiated in 529, they are the oldest of all the religious orders in the Latin Church. The male religious are also sometimes called the Black Monks, especially in English speaking countries, after the colour of their habits, although some, like the Olivetans, wear white. They were founded by Benedict of Nursia, a 6th-century Italian monk who laid the foundations of Benedictine monasticism through the formulation of his Rule. Benedict's sister, Scholastica, possibly his twin, also became a religious from an early age, but chose to live as a hermit. They retained a close relationship until her death.