Decrepitness is a word that describes the state of being old, weak, and in poor health. However, there are many antonyms to this word that describe the opposite. Vitality, for example, is a word that describes the state of being strong, lively, and full of energy. Youthfulness is another antonym for decrepitness, which is associated with being young, vibrant, and healthy. Strength is also an antonym, as it refers to the physical power and ability to accomplish tasks easily. Robustness, on the other hand, is an antonym that suggests a state of being healthy, sturdy, and enduring. All of these words are the opposite of decrepitness and indicate a state of being active, energetic, and healthy.