The word "恍然大悟" is formed from four characters: "恍" meaning sudden, "然" functioning as an adverbial suffix to indicate manner, "大" meaning great or full, and "悟" meaning realization or understanding. The combination "恍然" conveys suddenness, while "大悟" denotes a profound realization, so the phrase literally structures as "suddenly" modifying "great realization" to express the concept of abruptly achieving complete comprehension.