Methods are similar to functions in other programming languages which contains a set of statements. Usually methods are written when multiple calls are required to same set of statements which increases re-usuability and modularity.

How to define a method

Method name are always starts with a lowercase letter.

def methodName [( [arg [= default]]...[, * arg [, &expr ]])]
   #code  
end 

Example : 1

def greetings(name = "Foo") # defaulting name as foo 
   puts "Hello #{name}"
end
greetings "John"
greetings

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Example : 2

# Sum of two intergers in ruby
def sum(x , y)
   sum = x+y
   puts "Sum: #{sum}"
end

sum(10,20)

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