Infinite Sets. If you continue to study this subject you will find discussions about infinite sets, and the idea of different sizes of infinity. That subject has special names like Aleph-null (how many Natural Numbers), Aleph-one and so on, which are used to measure the sizes of sets.
For decades, glossy paper, the type used in magazines, was made using a white clay called kaolin (named after the Chinese region Kao-Ling where it was mined to produce porcelain).
Our dull/matte cover is a substantial paper with a smooth, non-shiny coating. It is a heavy 14pt stock well suited for detailed, crisp printing without sacrificing the ability to easily write on the paper. You can also add UV coating on the front of a dull/matte card to add pop to the side that isn't needed for writing.