Adjective + 的 + 天空
The noun 天空 (tiānkōng) means 'sky' and is a compound of 天 (heaven/day) and 空 (empty/space). It is used to describe the visible expanse above the earth and frequently appears with descriptive modifiers like 蓝色的天空 (blue sky) or 黑暗的天空 (dark sky).
今天的天空特别蓝,一朵云都没有。
jīntiān de tiānkōng tèbié lán, yì duǒ yún dōu méiyǒu.
The sky is especially blue today, without a single cloud.
夜晚的天空挂满了星星。
yèwǎn de tiānkōng guà mǎn le xīngxīng.
The night sky is covered with stars.
天空突然变暗了,好像要下雨。
Tiānkōng tūrán biàn àn le, hǎoxiàng yào xià yǔ.
The sky suddenly darkened — it looks like it's going to rain.