The word 'fairies' is late in origin; the earlier noun is fays, which now has an archaic and rather affected sound. This is thought to be a broken-down form of Fatae. The classical three Fates were later multiplied into supernatural ladies who directed the destiny of men and attended childbirths. 'Fay-erie' was first a state of enchantment or glamour, and was only later used for the fays who wielded those powers of illusion.

The term 'fairy' now covers a large area, the Anglo-Saxon and Scandinavian elves, the daoine sidhe of the Highlands, the tuatha de danann of Ireland, the tylwyth teg of Wales, the seelie court and the unseelie court, the wee folk and good neighbours and many others. The trooping fairies and the solitary fairies are included in it, the fairies of human or more than human size, the three-foot fairies and the tiny fairies; the domestic fairies and those that are wild and alien to man; the subterranean fairies and the water fairies that haunt lochs, streams or the sea. The supernatural hags, monsters and bogies might be considered to belong to a different category, and there are, of course, fairy animals to be considered.