psi; Ψ, ψ +

(Greek: the twenty-third letter of the Greek alphabet; Ψ, ψ)

The 23rd letter of the Greek alphabet (Ψ, ψ), represented in the English alphabet as ps.
psi phenomenon
1. A phenomenon that includes both psychokinesis and extrasensory perception.

The extrasensory mental processes involved in the alleged ability to send or to receive telepathic messages.

2. In parapsychology, this term refers to whatever it is that enables a person to perceive extrasensorially.

This word was added so you will know that there is no known connection with this psi and the Greek psi (Ψ, ψ). This psi is said to be a shortening and alteration of parapsychological or a shortening of psychic or parapsychic.

psi, p.s.i; measurement
Pounds per square inch.

This psi has been added to let you know that it has nothing to do with the Greek psi (Ψ, ψ).

You can see all of the letters of the Greek Alphabet on this page.