How do you spell Ardor

Available Definitions:
1)  n. - Heat, in a literal sense; as, the ardor of the sun's rays.
2)  n. - Warmth or heat of passion or affection; eagerness; zeal; as, he pursues study with ardor; the fought with ardor; martial ardor.
3)  n. - Bright and effulgent spirits; seraphim.