[kyberias]

Substitute e.g. Python or C++ for APL. Do you still think the articly should explain that "C++ is a programming language."

[goatlover]

It's probably because APL doesn't look anything like your typical PL.

[deathanatos]

Which — once you're acquainted with its existence — is the very thing that makes it instantly recognizable.

[sbmthakur]

No. I would settle for a full form and even that should be mentioned only once in the start.