Use "concavity" in a sentence

1. “There’s a concavity in the ground over there that’s about the right size and shape

2. His other hand moved slowly down her back, until it was in the concavity above her hips, then he pulled gently until her hips were pressed firmly against his

3. concavity should be defined (convexities and concavities present at welding are focal points for

4. As long as you were safe in your apartment, why rock the boat? Snowmelt and dope bubbled and hissed in the concavity of the spoon and let off oily steam