I don't think there's any one knock-down criterion, but there are several small things that add up: -Scala was intended to have strong FP and OO support from d

I don't think there's any one knock-down criterion, but there are several small things that add up: -Scala was intended to have strong FP and OO support from day 1 -Scala has very strong support for immutable values and persistent data structures. It's hard to do FP efficiently without these -Similarly, Scala has built in support for laziness to a significantly greater extent than most languages. This is arguably important because it supports immutability, there are some important mutable algorithms that have no efficient immutable equivalent without laziness -Strong lambdas (unlike, e.g., Python) -Many of the major Scala libraries are either written in a heavily functional style or support highly functional APIs, while libraries in most languages do not