Hey-day refers to a period of great success or popularity, often associated with youth or vitality. There are several synonyms for this term which include the following: golden age, peak, prime, pinnacle, zenith, climax, apex, acme, high point, flourishing period, top level and high-water mark. Each of these synonyms highlights a different aspect of a hey-day, whether it is a time of maturity and success, a peak of energy and activity, or a period of intellectual or artistic achievement. Ultimately, each synonym conveys a sense of vibrancy, dynamism, and excellence that characterizes a hey-day.