A church service (or a service of worship) is a formalized period of Christian communal worship, often held in a church building. Most Christian denominations hold church services on the Lord's Day (offering Sunday morning and Sunday evening services); a number of traditions have mid-week services, while some traditions worship on a Saturday. In some Christian denominations, church services are held daily, with these including those in which the seven canonical hours are prayed, as well as the offering of the Mass, among other forms of worship. In addition to this, many Christians attend services on holy days such as Christmas, Ash Wednesday, Good Friday, Ascension Thursday, among others depending on the Christian denomination.
The church service is the gathering together of Christians to be taught the "Word of God" (the Christian Bible) and encouraged in their faith. Technically, the church in "church service" refers to the gathering of the faithful rather than to the physical place in which it takes place. In most Christian traditions services are presided over by clergy wherever possible, but some traditions utilize lay preachers. Styles of service vary greatly, from the Anglican, Eastern Orthodox, Oriental Orthodox, Reformed (Continental Reformed, Presbyterian), Roman Catholic, and Lutheran traditions of liturgical worship to informal worship characterized by certain free church traditions, common among Methodists and Baptists, that often combine worship with teaching for the believers, which may also have an evangelistic component appealing to backsliders and the non-Christians in the congregation (cf. altar call). Quakers and some other groups have no formal outline to their services, but allow the worship to develop as the participants present feel moved.