firmament

例句：

1. 1.The firmament is a vast expanse of sky above the earth's surface.
   天穹是地球表面上方的广阔天空。
2. 2. The firmament is often depicted as a celestial body in mythology and religion.
   天穹在神话和宗教中经常被描绘为一个天体。
3. 3. The firmament is a source of inspiration for many artists who seek to capture the beauty of nature.
   天穹是许多艺术家寻求捕捉自然之美的灵感来源。