When modelling concurrency theory we often model the various things that can happen as interleaved. That is: given any two "events" and that have occurred, it must be that either occured first or occurred first. Models with true concurrency reject this notion of interleaving. Instead, they accept that events might truly happen at the same time.
In terms of CCS notation, the process , which performs and in parallel, is not seen as equivalent to the process , which nondeterministically chooses to perform first then , or the other way around.
Other names for true concurrency include:
Examples of models of true concurrency include: