What is the meaning of plastic

A?plastic?is a?material?that can change its shape. Many things are made of plastics, usually because making them the right shape is easy. There are many types of plastic. Some can be shaped only when they are freshly made; then they become hard. Others are?thermoplastic?and can be softened by heating them. These plastics can be used for?3D printing because the plastic will become soft enough to form into different shapes, and then become hard again when they cool down.