The term "young sky" can refer to a bright, clear, and new-looking sky. Its antonyms, on the other hand, can be words describing different types of skies that are opposite in appearance. For example, an overcast or cloudy sky, a smoky or hazy sky, or a dark or stormy sky can all be antonyms for young sky. Furthermore, a sky that is dull, faded, or aged-looking can also be an antonym for young sky. Therefore, the antonyms of the term "young sky" correspond to different kinds of skies that are not bright, clear, or new-looking, but rather dull, hazy, cloudy, or stormy.