The phrase "certain softness" means a gentle or delicate quality that is specific or well-defined in some way.
Sentences with «certain softness»
If you are going to sit for hours on a plane, then the material has to have a certain softness to it. (compressioncarl.com)
When you do find a smooth section of road to brave the Q7's acclaimed handling, you'll find that even in Sport mode there's a certain softness to the way the Q7 goes about its thing. (paultan.org)
There's a certain softness to the world of (monstervine.com)