As the other poster implied, it's the difference between a library of functions and an alphabet for composing functions. Concise symbols allow composition of "w

As the other poster implied, it's the difference between a library of functions and an alphabet for composing functions. Concise symbols allow composition of "words" in a way that longer names really don't. There's a practical language design side too - I don't think the right-to-left evaluation and accompanying concision and logical reading order would work otherwise. Maps in other languages are so clumsy and clunky and backwards compared to the APL equivalent.