The relative interior and closure in the L-fuzzy topology can represent the upper approximation set and the lower approximation set, respectively, which are the two most important concepts in the theory of covering generalized rough sets. In this report, we studied and introduced the concept of connectedness relative to a subbase. Such connectedness is weaker than that of the L-fuzzy topology, but they share many similar properties. These properties are in fact the generalization of the connectedness. So studying the connectedness relative to a subbase and its properties is fundamentally important not only in the theory of rough sets but also in the L-fuzzy topology itself.