Πατήρ, Υἱός, Ἅγιοῦ Πνεῦμα (Patēr, Huios, Hagion Pneuma)
* Πατήρ (Patēr): Father
* Υἱός (Huios): Son
* Ἅγιοῦ (Hagion): Holy (genitive singular of ἅγιος -hagios-)
* Πνεῦμα (Pneuma): Spirit
Note the use of the genitive case ("Hagion") with "Pneuma." This is because "Holy Spirit" is a single concept and the adjective "holy" modifies the noun "Spirit".