Plastic surgery has two branches, cosmetic surgery and reconstructive plastic surgery. Cosmetic surgery aims to improve the aesthetic appearance of a person, while plastic surgery may include this, or just the reconstruction (reconstructive surgery). Reconstructive plastic surgery aims to improve function; however, it may also involve trying to approximate normal appearance, but that is not its primary function. Reconstructive plastic surgery is often referred as simply reconstructive surgery.Some parts of the world completely separate cosmetic surgery and plastic surgery and term cosmetic surgery as elective surgery, non-essential surgery, surgery which the patient chooses to have; while plastic surgery is understood to mean surgery to reconstruct or improve appearance after injury or illness.