Concurrency is a Paradigm.

Concurrency is not parallelism.^[1]

Concurrency is a paradigm.

Programs designed to be parallel must employ the concurrent paradigm.

Parallelism implies Concurrency.

Concurrency does not imply Parallelism.

Concurrency is a paradigm.  Concurrency is often conflated with Parallelism.

Concurrency is simpler than Parallelism.  

Concurrency is not time-sharing.  

Concurrency is not memory-sharing.  

Concurrency is not thread safety.  

Concurrency is not priority inversion.

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[1] Rob Pike’s talk “Concurrency Is Not Parallelism” https://vimeo.com/49718712