Diesel engines have pistons that look different from the ones you'd see with a gas engine. There's a reason why that's the ...

It propels itself from the branch with the lower half of its body, forms quickly into an S, and flattens to about twice its normal width, giving its normally round body a concave C shape ...

In a ray diagram, a concave lens is drawn as a vertical line with inward facing arrows to indicate the shape of the lens.

In a ray diagram, a concave lens is drawn as a vertical line with inward facing arrows to indicate the shape of the lens.