I get that terms can change in meaning over time. I totally concede the point that complaining about the term &quot;regular expression&quot; being misused is a lost cause at this point. The term has graduated from a purely technical term to something that is colloquially used quite frequently. I find it unfortunate, but I&#x27;m not going to nitpick someone to death over that.<p>With that said, I absolutely take issue with using the term NFA to describe <i>anything</i> that is NP-complete. It&#x27;s just plain nonsense. The term &quot;NFA&quot; isn&#x27;t nearly as widely used as &quot;regular expression,&quot; and it is a very technical term with very specific technical implications.<p>&gt; it isn&#x27;t actually wrong to say that &quot;This RE engine uses an NFA algorithm on regular expressions.&quot;<p>This is exactly the problem. It <i>is</i> wrong to say that Perl uses an NFA algorithm. It literally cannot be true because Perl implements features that are NP-complete.<p>This is exactly what happens when people get sloppy with their teminology. They start bending the meaning of words to say something that doesn&#x27;t make any sense. As a result, those of us who aren&#x27;t as informed end up getting extremely confused.<p>&gt; or to get people to stop calling their so-called (but not really) RE engines, NFA implementations.<p>In a discussion like the one in this thread, where the distinction <i>ACTUALLY MATTERS</i>, it is absolutely worth pointing out.<p>&gt; Good luck convincing Java, JavaScript and Python to make backwards incompatible changes so we can restore language terminology!<p>This is such a bad argument and such a huge straw man. Do you think I&#x27;m on some crusade to fix terminology? No. That&#x27;s stupid and a waste of time. The only reason I brought this up is because your initial comment in this thread suggested (to me) that you were confused about the terminology being used! Why? Because wolfgke used the term NFA correctly: &quot;An NFA does not use backtracking.&quot; But you chimed in with stuff about backreferences and &quot;real&quot; regex engines. What gives? I don&#x27;t know, but it seemed like a clarification was in order to me.