**Final Edit**: I just realized that when use the word "parallelism", it's almost `parallelism==ILP`, I originally thought even a single instruction could be divided into several phrases, and at that level there would be some parallelism, but then I realized this has no meaning. Both my title and my example didn't mentioned anything about more than one threads' parallelism as done by HyperThreading, so @user110971's is the correct answer, without doubt anymore. (In the philosophical level, I just need a base-case condition to return my recursiveness of finding the deepest part of parallelism)

**Edit3:** I made a graph for my **Edit2**, and I found [this video on YouTube about HyperThreading](https://www.youtube.com/watch?v=lrT9Bl0MCXQ) useful.
[![enter image description here](https://i.stack.imgur.com/TiwnU.png)](https://i.stack.imgur.com/TiwnU.png)

**Edit2:** In short, for my question I adopt the definitions on Wikipedia, and for the definition of the terms:

* Parallel: Two threads, run independently, at any physical instant. So one thread won't interrupt the other, at any instant.
* Concurrent: Two threads, run independently, interleavedly is allowed, i.e. not restricted to parallel, and one can interrupt the other.
* In short, for me and Wikipedia writers, Concurrent includes Parallel. Thanks.

**Edit:** Just to be clear, for me parallelism means true parallelism, I add a "true" for it because people I talked to tend to think `parallel==concurrent`. (See my second link)

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Is it true that on modern processor, "true" [parallelism](https://en.wikipedia.org/wiki/Parallel_computing) is possible on a single core? I asked elsewhere but didn't get a confirming answer. What I want to know is e.g. whether at t=0, two instructions are fetched and executed. At the same physical instant.

My question came from [here](https://en.wikipedia.org/wiki/Concurrent_computing#Introduction):

> 
> parallel computing is impossible on a (one-core) single processor, as only one computation can occur at any instant (during any single clock cycle).
> 
> 
>