module Identifier
  statement1
  statement2
  ...........
end

#!/usr/bin/ruby

# Module defined in trig.rb file

module Trig
  PI = 3.141592654
  def Trig.sin(x)
  # ..
  end
  def Trig.cos(x)
  # ..
  end
end

#!/usr/bin/ruby

# Module defined in moral.rb file

module Moral
  VERY_BAD = 0
  BAD = 1
  def Moral.sin(badness)
  # ...
  end
end

require 'trig.rb'
require 'moral'

y = Trig.sin(Trig::PI/4)
wrongdoing = Moral.sin(Moral::VERY_BAD)

module Week
  FIRST_DAY = "Sunday"
  def Week.weeks_in_month
   puts "You have four weeks in a month"
  end
  def Week.weeks_in_year
   puts "You have 52 weeks in a year"
  end
end

#!/usr/bin/ruby
require "support"

class Decade
include Week
  no_of_yrs=10
  def no_of_months
   puts Week::FIRST_DAY
   number=10*12
   puts number
  end
end
d1=Decade.new
puts Week::FIRST_DAY
Week.weeks_in_month
Week.weeks_in_year
d1.no_of_months

Sunday
You have four weeks in a month
You have 52 weeks in a year
Sunday
120

module A
  def a1
  end
  def a2
  end
end
module B
  def b1
  end
  def b2
  end
end

class Sample
include A
include B
  def s1
  end
end

samp=Sample.new
samp.a1
samp.a2
samp.b1
samp.b2
samp.s1