Etymology

psi

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Today it means: The twenty-third letter of Classical and Modern Greek and the twenty-fifth letter of Old and Ancient Greek. Full definition →

Middle English psi ← Latin psī ← Ancient Greek ψεῖ
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psi · noun1

  1. Ancient Greek · derived fromψεῖ
  2. Latin · derived frompsī
  3. Middle English · inherited frompsi
  4. English todaypsi

From Middle English psi, from Latin psī, from Ancient Greek ψεῖ (pseî), the name for the twenty-third letter of the alphabet (Ψ, ψ).

psi · symbol2

Initialism of pounds per square inch.

Etymology from Wiktionary, CC BY-SA 4.0.