What is the difference between solid wood, engineered wood and WPC interior doors?

Solid wood doors use natural timber (oak, ash, walnut) and give the richest grain, but they move most with humidity. Engineered doors bond a stable core (LVL, finger-joint or solid-core board) with veneer or laminate, so they resist warping far better. WPC (wood-plastic composite) is fully waterproof, termite-proof and needs almost no maintenance, which is why it now dominates bathrooms, kitchens and tropical projects.