Singular - Ás, Plural - Ases.
Old High Germanic - Os Modern English - Ase,
The Aesir are one of the two principal pantheons of Gods and Goddesses in the native Germanic religion. They include many of the major deities, such as Odin, Frigga, Thor, Balder and Tyr. The Goddesses of the Aesir are known as the Asynjur, and although the term Aesir is used as the general name for all of the gods and goddesses, a second clan of Gods, known as the Vanir are also greatly honoured; Freyr and Freyja are the foremost of the Vanir and they reside amongst the Aesir in Asgard. The Aesir are generally the deities of consciousness and are more associated with fire, air, war, power and the passionate mechanical aspects of being; whereas the Vanir are associated with earth, water, the natural and organic and are mainly connected with fertility, joy and peace, although these are by no means firmly set boundaries.
The Aesir stayed forever young by eating the golden apples kept by Idunna ,the Goddess governing the regenerative powers of eternal youth and spring fertility. Unlike the gods of some other religions, the Aesir and Vanir are not immortal; many will die at Ragnarok with some very few exceptions who will survive and rebuild the glory of the Asgard.
Our religious teachings tell us that the Æsir and the Vanir once held a war, which, since their battle-might was equal, their great battles ended in a draw. The truce was settled by the creation of the being Kvasir and the trading of hostages: Odin’s brother Hoenir and the giant Mimir went to the Vanir, and Njord and Frey were sent among the Æsir (Freyja seems to have come along of her own choice), where, according to Ynglinga saga, they held the role of “priests”.
It is interesting to speculate if the interactions described as occurring between Aesir and Vanir reflect the types of interaction common to various Germanic clans at the time. According to another theory, the cult of the Vanir (who are mainly connected with fertility and relatively peaceful) may be of an older date, and that of the more warlike Aesir of later origin, so the mythical war may perhaps mirror a historic religious conflict.
(In alphabetical order):
Freyja, a Vanir hostage
Freyr, a Vanir hostage
Njord, a Vanir hostage
Art: Thor wades while the Aesir ride by Frølich