This article lists concurrent and parallel programming languages, categorizing them by a defining paradigm. Concurrent and parallel programming languages involve multiple timelines. Such languages provide whose behavior is defined by a parallel execution model. A concurrent programming language is defined as one which uses the concept of simultaneously executing processes or threads of execution as a means of structuring a program. A parallel language is able to express programs that are executable on more than one processor. Both types are listed, as concurrency is a useful tool in expressing parallelism, but it is not necessary. In both cases, the features must be part of the language syntax and not an extension such as a library (libraries such as the posix-thread library implement a p