Class, Instance and Singleton methods

There are three types of methods in Ruby and I always get them confused. Here, for my future reference, is what I currently think they mean.

Class methods

Methods which can be called directly on a class.

Time.now
Monkey.find(:all)

Instance methods

Methods which can be called on any instance of that class.

@widget.to_s
Time.now.to_f

Singleton methods

Methods which can be called only on a specific instance of that class.

chicken = Chicken.new
class << chicken
  def hide
    # ...
  end
end
chicken.hide