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Halloween is usually a time for superstition and celebration that occurs on the evening of October 31st. Currently, Halloween is celebrated globally and reflects on the integration of several beliefs. It has become mostly a commercial and secular holiday in the 21st Century. Most people celebrate this tradition by telling tales of ghosts and witches as well as dressing in different mystifying costumes. It takes place between fall and winter and also, life and death. Children trick- or -treat. That is, they go from home to home collecting candy or in some communities, cash. Some communities also carry out parties or parades. Notably, on this day, lots of death have occurred resulting from both natural and unnatural causes. 

Halloween originated as an ancient holiday of Samhain. It was first celebrated by the Celts who lived in what is now Northern France, The United Kingdom, and Ireland over 2,000 years ago. The Samhain was one of the four Gaelic festivals that got -celebrated on the 31st of October. The day symbolized the close of summer and harvest, and the start of winter. During this time it was thought the two worlds, that of the living and the dead had a thin boundary, and that the ghosts of the dead came back to earth at night. At that time, the season of winter was associated with death. 
In celebration of the events, the Celtic priests (druids) set up huge bonfires, parades and dressed up as supernatural beings. The costumes comprised of animal skins and heads, and during the time of celebrations, they tried to tell the fortunes of one another. In Christianity, November 1st began to be celebrated in honor of all Saints and Martyrs (All saints day or All-hallows). Which got moved from May 13th by Pope Gregory III. With November 2nd being honored as a day of the dead (All souls day). The celebrations of all souls day and those of the Samhain were alike. 
At the start of the 9th century, the beliefs of Christianity had already extended into the Celtic communities. This resulted in blending and displacing the original Celtic rites. 
The Samhain was devised and known as the all-hallows eve and ultimately Halloween.
Traditions of Halloween
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The traditions that came with dressing up during Halloween has roots in the Celtic and European cultures. For people not to be recognized by the ghosts, they put on masks and left their homes so that the ghosts could think of them as fellow spirits. In addition to this, they would try and keep off ghosts from their homes by placing bowls with food outside their houses. 
The trick or treat tradition came about from the Christian practice where people would go around from house to house on all saints day asking for food. In return, on all souls day, they prayed for the dead. 

 In addition to these Celtic traditions, pumpkin carving got done. Here, carvings were done into vegetables, preferably pumpkins and turnips, and inserted lightning in them. This was to light their way home for the good spirits.