The word ceramic is derived from the Greek word keramikos, "having to do with pottery". The term covers inorganic nonmetallic materials whose formation is due to the action of heat. Up until the 1950s or so, the most important of these were the traditional clays, made into pottery, bricks, tiles and the like, along with cements and glass.
Historically, ceramic products have been hard, porous, and brittle. Technical Ceramics can also be classified into three distinct material categories:

Oxides: Alumina, zirconia
Nonoxides: Carbides, borides, nitrides, silicides
Composites: Particulate reinforced combinations of oxides and nonoxides.

Ceramic materials can be crystalline or amorphous. They tend to fracture before any plastic deformation takes place, which results in poor toughness in these materials. Additionally, because these materials tend to be porous, the pores and other microscopic imperfections act as stress concentrators, decreasing the toughness further, and reducing the tensile strength. These combine to give catastrophic failures, as opposed to the normally much more gentle failure modes of metals.   _{Your Comment}