A definitive stamp is a postage stamp that is part of regular issue of a countries' stamps which is available for sale by the post office for an extended period of time. In India, there are 11 definitive series are issued. Every Definitive stamp series are based on a theme. 

1st Definitive series - Archeological series, 2nd Definitive series - Five year Plan, 3rd Definitive series - Map of India, 4th & 5th Definitive series - Agriculture and Tourism, 6th Definitive series - Rural Prosperity, 7th Definitive series - Science and Technology, 8th Definitive series - Family Planning and Personality, 9th Definitive series - Natural Heritage of India, 10th Definitive series - Builders of Modern India, 11th Definitive series - Maker's of India