In generative syntax, binding theory is a theory on A-binding.
Binding theory consists of the three conditions in (i).
A An anaphor is bound in its binding domain. B A pronominal is free in its binding domain. C An R-expression is free.
a [+anaphor, -pronominal] = anaphor b [+anaphor, +pronominal] = PRO c [-anaphor, -pronominal] = R-expression d [-anaphor, +pronominal] = pronominal