DEFINITION: Samhain

It seems that there are several 'Definitions' for Samhain. Here are a few from the my research...

noun
a festival of the ancient Celts, held around November 1 to celebrate the beginning of winter.

From here...
http://dictionary.reference.com/browse/samhain

Samhain is a cross-quarter sabbat; a night when the veil between this world and the next is the thinnest. It is a time to honor those who've died during the old year just leaving, as well as all ancestral spirits. [excerpt]

From here...
http://en.mimi.hu/esoteric/samhain.html

Samhain is the Celtic harvest festival which occurs on October 31 or November 1. It marked the ending of the fertile period of the year and the beginning of winter. During the winter period, it was believed that a path to "another world" was open, allowing spirits and such to visit people at night.

From here...
http://atheism.about.com/library/glossary/general/bldef_samhain.htm

DEFINITION: Halloween

Noun: hal·low·een/ˌhaləˈwēn/

The night of October 31, celebrated by children who dress in costume and solicit treats door-to-door.

Halloween is traced back to many harvest and "end of summer" celebrations. It is a mishmash of many different traditions. From the Roman feast of Pomona, the Celtic festival of Samhain, and the Scottish custom of souling custom (which involves carving turnips into lanterns as a way of remembering the souls held in purgatory).

All Hallows Eve is first recorded in 1556 as a celebration the night before All Hallows Day (a much older tradition).

More here:
http://en.wikipedia.org/wiki/Halloween