1. Plural of psi; the twenty-third letter of the Greek alphabet.
Usage: Used in mathematics, science, and Greek contexts.
2. Plural of psi; a unit of pressure equal to one pound per square inch.
Usage: Technical/scientific usage; abbreviation for pounds per square inch.

Examples

• The Greek alphabet includes alphas, betas, and psis.
• The tire pressure was measured at 32 psis.
• In physics equations, psis often represent wave functions.
• The pressure gauge showed the reading in psis.
• Students learning Greek must memorize all the psis and other letters.