Definition:
Plasticity (noun) refers to how flexible a clay or clay body is. Any particular clay's plasticity is greatly influenced by the clay's particle size, water content, and aging.
It is easy to find out how plastic (adjective) a clay is. Make a coil of the clay and then wrapped it around your finger. A plastic clay will not crack or break. Non-plastic clays will.
Examples:
Small organisms can grow within clay; these organisms help increase a clay's plasticity. (noun)
Ball clays are very plastic, but they shrink a great deal. (adjective)