Plastic, pliable, pliant, ductile, malleable, adaptable are applied to things and to persons regarded as material susceptible of being modified in form or nature.
Something plastic has the quality (as of wax, clay, or plaster) of being soft enough to be molded or to receive an impression yet capable of hardening into a final form.
Something pliable or pliant has the quality (as of willow twigs) of being supple enough to be easily bent or manipulated and therefore yielding without resistance. Pliable, in extended use, usually suggests the imposition of or submission to another's will.
Pliant, on the other hand, suggests flexibility rather than obedience.
Something ductile has the quality of a tensile metal (as copper) of being tenacious enough to be permanently drawn out or extended, or of water, of being made to flow through channels. In extended use ductile often approaches plastic and pliant but it may have distinctive connotations directly derived from its literal senses, such as quick responsiveness (as distinguished from submissiveness) to influences that would form, guide, or fashion.
Sometimes fluidity within bounds is connoted.
Something malleable is literally or figuratively capable of being beaten or pressed into shape, especially after being conditioned (as by heating).
Something adaptable is capable of being modified or of modifying itself to suit other conditions, other needs, or other uses.
As applied to persons the term implies sometimes a pliant, but more often an accommodating, disposition and a readiness to make one's habits, one's opinions, and one's wishes correspond to those of one's present society or environment.