"Happiest birthday" is an expression used to wish someone an exceptionally joyful and fulfilling birthday.
While "happy birthday" is the standard greeting, "happiest birthday" aims to amplify the sentiment, expressing a desire for the most joyous celebration possible. Grammatically, using the superlative "happiest" emphasizes a wish for an even greater level of happiness on the birthday compared to just "happy." It's a way to convey extra warmth and affection to the birthday celebrant.
For example, you might say to a close friend or family member: "I wish you the happiest birthday filled with love, laughter, and all your favorite things!"
