A shadow because there no bird that you can see
Answer:
umm what this might be related
<em>a door with glass panes throughout its length. French door could be a pair or not.</em>
Explanation:
Bio means life
Geo means earth
Chemical is a substance produced or used by chemistry.
And cycle is a series of events that are regularly repeated in the same order.
There are more than one definitions if the last two but I picked the ones I thought were best. This is my guess. Hope I helped!