ETYM Old Eng. trinitee, French trinité, Latin trinitas, from trini three each. Related to Trinal.
1. The union of three persons (the Father, the Son, and the Holy Ghost) in one Godhead, so that all the three are one God as to substance, but three persons as to individuality.
2. Any union of three in one; three units treated as one; a triad, as the Hindoo trinity, or Trimurti.
3. Any symbol of the Trinity employed in Christian art, especially the triangle.
Fresco by Masaccio about 1428 (Sta Maria Novella, Florence), the first painting to use the techniques of artificial perspective developed by Brunelleschi. In its original state it would have produced a stunning effect of three-dimensionality but time and air pollution have eroded its color and tonal values.
In Christianity, the union of three persons—Father, Son, and Holy Ghost/Spirit—in one godhead. The precise meaning of the doctrine has been the cause of unending dispute, and was the chief cause of the split between the Eastern Orthodox and Roman Catholic churches. Trinity Sunday occurs on the Sunday after Pentecost (Whitsun).