Ceramics vs Pottery
Apparently the word ‘ceramic’ derives from the Greek ‘keramikos ‘meaning ‘of pottery’ or ‘for pottery’. Hence both words refer to objects made of clay and hardened by heat. In archeology, pottery is a form of ceramics, specifically clay containers (pots), with other articles referred to as ‘terracottas’. Others say that, technically, all non-metallic materials that are permanently hardened by heating, including glass and glazes, are ceramics.
To further complicate matters, there are 3 classes of pottery; earthenware, stoneware and porcelain, which differ in the temperature to which they are fired. Porcelain also differs in the mixture used; small amounts of glass, granite, and feldspar minerals are ground up with fine, white clay and then mixed with water.
So technically, buttons can be made of ceramics, but are not pottery, despite sometimes being called that.