What are the meanings of the terms 'necromancy and nigromancy?

NECROMANCY - is the practice of magic involving communication with the dead - either by summoning their spirits as apparitions, visions or raising them bodily - for the purpose of divination, imparting the means to foretell future events, discover hidden knowledge, to bring someone back from the dead, or to use the dead as a weapon. Sometimes referred to as ''Death Magic'', the term may also sometimes be used in a more general sense to refer to black magic or witchcraft. NIGROMANCY - meaning black magic or black divination, was a highly intricate form of ritual magic, whose educated adherents summoned demons with magic circles drawn in blood and long Latin recitations replete with words such as conjuro, adjuro, and exorcizo.