A missionary is a member of a religious group sent into an area to proselytize and/or perform ministries of service, such as education, literacy, social justice, health care, and economic development. The word "mission" originates from 1598 when the Jesuits sent members abroad, derived from the Latin "missionem" (nom. "missio"), meaning "act of sending" or "mittere", meaning "to send". The word was used in light of its biblical usage; in the Latin translation of the Bible, Christ uses the word when sending the disciples to preach in his name. The term is most commonly used for Christian missions, but can be used for any creed or ideology. 

A Christian missionary can be defined as "one who is to witness across cultures". The Lausanne Congress of 1974, defined the term, related to Christian mission as, "to form a viable indigenous church-planting movement". Missionaries can be found in many countries around the world. 

Jesus instructed the apostles to make disciples of all nations. This verse is referred to by Christian missionaries as the Great Commission and inspires missionary work. 

The New Testament-era missionary outreach of the Christian church from the time of St Paul expanded throughout the Roman Empire and beyond to Persia (Church of the East) and to India (Saint Thomas Christians). During the Middle Ages the Christian monasteries and missionaries such as Saint Patrick (5th century), and Adalbert of Prague (ca 956-997) propagated learning and religion beyond the European boundaries of the old Roman Empire. In 596, Pope Gregory the Great (in office 590-604) sent the Gregorian Mission (including Augustine of Canterbury) into England. In their turn, Christians from Ireland (the Hiberno-Scottish mission) and from Britain (Saint Boniface (ca 675-754), and the Anglo-Saxon mission, for example) became prominent in converting the inhabitants of central Europe.
who is a missionary?
 member of a religious group sent into an area to proselytize and/or perform ministries of service, such as education, literacy, social justice, health care, and economic development