Whats the difference between Plexiglass and Plexiglas®?

These two terms are pronounced the same and spelt almost identically, however, Plexiglass is the genericized trademark or proprietary emponym that has become synonymous with acrylic sheeting in most of Europe and North America whereas Plexiglas® is the brand name for acrylic sheets manufactured by Röhm GmbH in Germany. Whilst Plexiglass has become the generic trademark for acrylic sheets in Europe and North America, the brand name Perspex® is synonymous with acrylic sheeting in the UK.