Vitreous is the thick, transparent substance that fills the centre of the eye.
From the nature.com
Light travels fastest in a vacuum, and ratio of this velocity to that in a transparent substance is called the refractive index.
From the newscientist.com
It was in the Roman glassmaking center at Trier, now in modern Germany, that the late-Latin term glesum originated, probably from a Germanic word for a transparent, lustrous substance.
From the en.wikipedia.org
He should commit to work in an open, bipartisan manner on new legislation that would earn public support both for its substance and through the transparent process by which it is crafted.
From the time.com
When the substance is only a few of these layers thick, though, it is known as graphene and is transparent.