In this paper, for any non-empty subset C of a pseudo
BCI-algebra X, the concept of p-closure of C, denoted by C(pc), is
introduced and some related properties are investigated. Applying
this concept, a characterization of the minimal elements of X is
given. It is proved that C(pc) is the least closed pseudo BCI-ideal of X
containing C and K(X) for any ideal C of X. Finally, by using the
concept of p-closure, a closure operator is introduced.