Solidity supports multiple inheritance by copying code including polymorphism. Even if a contract inherits from multiple other contracts, only a single contract is created on the blockchain; the code from the parent contracts is always copied into the final contract.

Here is an example to demonstrate inheritance:

contract sample1 
{ 
    function a(){} 

    function b(){} 
} 


//sample2 inherits sample1 
contract sample2 is sample1 
{ 
    function b(){} 
} 

contract sample3 
{ 
    function sample3(int b) 
    { 

    } 
} 

//sample4 inherits from sample1 and sample2 
//Note that sample1 is also parent of sample2, yet there is only a single instance of sample1  
contract sample4 is sample1, sample2 
{ 
    function a(){} 

    function c(){ 

        //this executes the "a" method of sample3 contract 
        a(); 

        //this executes the 'a" method of sample1 contract 
        sample1.a(); 

        //calls sample2.b() because it's in last in the parent contracts list and therefore it overrides sample1.b() 
        b(); 
    } 
} 

//If a constructor takes an argument, it needs to be provided at the constructor of the child contract. 
//In Solidity child constructor doesn't call parent constructor instead parent is initialized and copied to child 
contract sample5 is sample3(122) 
{ 

}