Methods

def / end, and the implicit return

Swift declares a function with func. Ruby uses def, closed with end — same as every other Ruby block:

def greet(name)
  "Hello, #{name}!"
end

Look closely: there's no return keyword in that method, yet it hands back the greeting. This is the single biggest habit to build: a Ruby method automatically returns the value of the LAST expression it evaluates. You can write return explicitly, and you will for early exits — but for the normal "compute a value and hand it back" case, idiomatic Ruby leaves return off entirely.