what's plasticity? when is this word used?

Native speaker’s answer
Rebecca
"Plasticity" refers to the quality of being easily shaped or molded. So if you were to describe a thing as being very plastic, you are saying that it is easily manipulated or shaped. Synonyms include "pliability" and "flexibility." Ex: Slime is very plastic and easy to shape, so children love playing with it. Ex: Children's minds are very plastic, so it's very important to educate them well while they are young.