The Shamrock,in Irish "Seamróg", symbolises the Trinity, that is, the Christian idea that there is One God but Three Persons in the One God, Father, Son and Holy Spirit. Before the Christian era it was a sacred plant of the Druids of Ireland because its leaves formed a triad. Famous stories tell of how St. Patrick used the shamrock in his teaching. Preaching in the open air about God and the Trinity, he illustrated the meaning of the Three in One by plucking a shamrock from the grass growing at his feet and showing it to his congregation. Just as the shamrock is one leaf with three parts, so God is one entity with three Persons.

The legend of the shamrock is also connected with that of the banishment of the serpent tribe from Ireland by a tradition that snakes are never seen on shamrocks and that it is a remedy against the stings of snakes and scorpions. The shamrock was a sacred plant for the Druids, and three was a mystical number in the Druidic religious tradition. It is probable that St. Patrick was aware of the significance of using a shamrock to illustrate this spiritual metaphor.

Believe it or not, the colour of St. Patrick was not actually green, but blue! In the 19th century, however, green came to be used as a symbol for Ireland. Thanks to plentiful rain and mist, the 'Emerald Isle' is indeed green year-round, which was probably the inspiration for the national colour.

The harp is an ancient musical instrument used in Ireland for centuries. It is also a symbol of Ireland (and of course of Guinness!). Harpists, who were often blind, occupied a honoured place in Irish society and, together with bards (or poets) played an important role in the social structure, supported by chieftans and kings. O'Carolan was one of the most famous harpists, and many Irish melodies inspired by him survive to this day.

There is custom to kiss the Blarney Stone on this day. This stone is set on the wall of the Blarney Castle Tower in a village named Blarney in Ireland. Any one who kisses the Blarney Stone is supposed to receive the gift of 'persuasive eloquence' (the ability to speak convincingly). It is believed that St. Patrick had a winning personality that enabled him to fulfil his mission of converting almost the whole of Ireland into Christianity.

There are numerous customs associated with this occasion some of which are followed by the people of Irish descent settled in different parts of the world.

Shamrock leaves are worn on the shoulder on this day to remember St. Patrick.

People exchange Irish - Gaelic greetings.

Little girls wear green ribbons and the boys wear a harp badge.

Shillelaghs are displayed and used for decorations.

People attend mass in the morning and St. Patrick Day parades are held in the afternoon.

Men follow a quaint ritual of the Drowning of the Shamrock. A shamrock leaf is dipped in whiskey and thrown over the left shoulder.