Felicity is a state of happiness or the quality of joy. Sitting on the roof with a telescope and iced tea on a clear, starry night is one way to find perfect felicity — a happy place.
Felicity comes from the Latin fēlīcitās, meaning "happiness." A synonym for felicity is "blissfulness." People, places, and things can have felicity: "His personality was so warm and full of felicity that we felt at ease the minute we met him." Or you can be in a state of felicity: "A full stomach, a fluffy couch, and the felicity of a Sunday-afternoon nap."