Symbol φ The 21st letter of the greek alphabet.
in Burmese folk religion, any of a group of spirits that are the objects of an extensive, probably pre-Buddhist cult; in Thailand a similar spirit is called phi. Most important of the nats are a group collectively called the "thirty-seven," made up of spirits of human beings who have died violent deaths. They are capable of protecting the believer when kept properly propitiated and of causing harm when offended or ignored.
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