A company can be a private limited company and also a 
government aided company .
An Organisation is a joint venture and run by many people 
and run  by direct or indirect investments
An industry is the place where employees undergo the work 
for the organisation where production takes place

A company is any form of business wheather small or large. 
Generally the term "Company" indicates a particular kind of 
business dealing in a very particular product.
Orgnisation is the larger form and generally comprises a 
number of companies.
Industry is the combination of companies in same line of 
business. Ex: Steel Industry includes all steel companies .

Hi Priya, ur definition of Industry is horrible. Rest are 
acceptable to some extent.

And for you Om P - Ur definition of industry is partially 
right - instead of using the term "companies" u should use 
the term "FIRMS" there. and the definition of organization 
is wrong..

Go and check the details in Harvard Business Review. they 
provide the best definition...