zone of proximal development (or "zpd")

Vygotsky 's term for an environment that supports learning.  In the zpd of infancy, for example, adults speak to the child before the child is able to understand saying things like, "It's chilly here.  That's why we have to bundle up," even though the infant is not yet know these phrases.  Neverthless, hearing things
like this over and over assists the development of the child's ability to speak.