concave

US /ˈkɑːn.keɪv/
UK /ˈkɑːn.keɪv/
"concave" picture
1.

konkav, hohl

having an outline or surface that curves inward like the interior of a circle or sphere

:
The spoon has a concave shape.
Der Löffel hat eine konkave Form.
The lens of the telescope is concave.
Die Linse des Teleskops ist konkav.