Sanity.
Bits of rolled-up rubber shed by the tires of race cars that accumulate at the edges of the track, especially at the corners.
Any of several children's games played with small balls (made of marble or more commonly glass).
Conscious understanding of something.
That which is detected by the five senses; not necessarily understood (imagine looking through fog, trying to understand if you see a small dog or a cat); also that which is detected within consciousness as a thought, intuition, deduction, etc.
Vision (ability)
The organisation, identification and interpretation of sensory information.
Acuity