The boundary of a convex set is always a convex curve. The intersection of all convex sets containing a given subset A of Euclidean space is called the convex hull of A. It is the smallest convex set containing A.
Rector (ecclesiastical) A rector is, in an ecclesiastical sense, a cleric who functions as an administrative leader in some Christian denominations, and in Islam. In contrast, a vicar is also a cleric but functions as an assistant and representative of an administrative leader.
As the original notion a vicar is of earthly representative of God or Christ  but also used in sense of person acting as parish priest in place of a real parson. The title is now used in Catholicism to refer to the bishops and more specifically to the Bishop of Rome (the pope).s the original notion a vicar is of earthly representative of God or Christ  but also used in sense of person acting as parish priest in place of a real parson. The title is now used in Catholicism to refer to the bishops and more specifically to the Bishop of Rome (the pope).