The noun form of ‘happy’ is ‘happiness’.
Happiness refers to a state of well-being and contentment. It embodies the feelings of joy, satisfaction, and positivity that arise from various life experiences. While ‘happy’ describes the emotional state of an individual, ‘happiness’ captures the overall essence and enduring quality of that state. For instance, when we say someone is happy, we refer to their current mood, but when we talk about happiness, we might be discussing a broader aspect of their life or the general sense of fulfillment they experience.