The Free On-line Dictionary of Computing (30 December 2018):
A collection of (probably heterogeneous) automata whose
distribution is transparent to the user so that the system
appears as one local machine. This is in contrast to a
network, where the user is aware that there are several
machines, and their location, storage replication, load
balancing and functionality is not transparent. Distributed
systems usually use some kind of client-server organisation.
Distributed systems are considered by some to be the "next
wave" of computing.
Distributed Computing Environment is the Open Software
Foundation's software architecture for distributed systems.