A computer program or routine is described as reentrant if it is designed in such a way that a single copy of the program's instructions in memory can be shared by multiple, separate users, object classes, or processes.
A computer program or routine is described as reentrant if it can be safely called recursively or from multiple tasks. This is not the same as being designed in such a way that a single copy of the program's instructions in memory can be shared by multiple, separate users, object classes, or processes.