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Functions are defined with equations — no function or def keyword:

add :: Int -> Int -> Int
add a b = a + b

Application is just whitespace — no parens needed: add 3 4 (not add(3, 4)).

Pattern-matching across multiple equations:

factorial :: Int -> Int
factorial 0 = 1
factorial n = n * factorial (n - 1)

The compiler tries equations top to bottom. First match wins.

Currying: every function takes one argument and returns a new function. add :: Int -> Int -> Int is really Int -> (Int -> Int). add 3 returns a function that adds 3 to its arg. Lets you partially apply naturally:

addThree = add 3
map addThree [1, 2, 3]   -- [4, 5, 6]