also: プシー
The 23rd letter of the Greek alphabet (Ψ, ψ). Used as a symbol in physics, mathematics, psychology, and other sciences.
Psi is the 23rd letter of the Greek alphabet.
In quantum mechanics, ψ represents the wave function.
From Greek ψεῖ (pseî), via English 'psi'. The Japanese readings プサイ and プシー reflect different English pronunciations.