Apse: Semicircular recess covered with a hemispherical vault at the back of the Sanctuary.
Archdioceses: Territory administered by an Archbishop. (Archdioceses: called as such due to size, historical significance or both)
Arch-presbyteral: A church holding first rank among the churches, its Parish priest being called Archpriest.
Basilica: Originally a Roman Royal Palace. In our case it denotes the importance of the particular church building usually given certain ceremonial privileges by the Pope.
Benefices: Properties given as a gift by the Pope to Bishops or Priests or even to Cathedrals in the past, for services rendered. During the Council of Trent, these were curtailed.
Cathedral: An important religious building for worship that is the seat of the Bishop or Archbishop of the Dioceses or Archdioceses.
Chapel: Actually part of a larger church with an altar of its own, it came to mean a smaller place of Christian worship other than church, parish church or cathedral even if free standing, sometimes one attached to a private house or institution.
Church: Building for public Christian worship.
Co-Cathedral: There were special circumstances in Malta when the new City of Valletta was built. With a Cathedral seat of the Bishop existing in the old city of Mdina, benefices could not be transferred to a new Cathedral and so St.John's in Valletta served and still does, as the Liturgical centre together with St.Paul's in Mdina.
Collegiate: A church served and administered by a college of canons, similar to a cathedral, although not the seat of a bishop.
Dioceses: Territory administered by a Bishop, an Archdiocese being under an Archbishop.
Matrice: From Latin 'Mater' meaning Mother. Refers to a church from whose jurisdiction sprang other parish churches even in the same town.
Nave: the central part of a church building, intended to accommodate most of the congregation.
Oratory: Small chapel for private or semi-public worship. Usually constructed by or for special groups within the parish.
Parish: Subdivision of a Diocese or Archdiocese having its own church and clergy with a Pastor or Parish Priest in charge. (Archpriest is a Parish priest of higher rank in charge of an Arch-presbyteral church or of a Basilica).
Parvis: An enclosed, usually raised area in front of a cathedral or church, sometimes surrounded with colonnades or porticoes.
Pastoral Centre: Building used for teaching catechism and for meetings by religious groups, many times also serving as a Church until a proper one is built, most probably becoming a Parish Church soon after.
Perpetual Adoration: Nowadays many old chapels are being used for the Perpetual (continuous) Adoration of the Blessed Sacrament where the Sacred Bread is exposed in a Monstrance and people take turns to do silent worship. These chapels and new ones opened for the purpose are open to the faithful on different schedules or all day long.
Sanctuary: I will use this word in two meanings: 1. The Holiest area of a church where the main liturgy is usually celebrated. 2. A church built on a holy spot, usually a place of pilgrimage.
Transepts: The two parts forming the arms of the cross shaped plan of a church, projecting at right angles from the nave close to the Sanctuary.