Surgery is a medical specialty that uses operative manual and instrumental techniques on a person to investigate or treat a pathological condition such as a disease or injury, to help improve bodily function, appearance, or to repair unwanted ruptured areas. The act of performing surgery may be called a surgical procedure, operation, or simply "surgery". In this context, the verb "operate" means to perform surgery. The adjective surgical means pertaining to surgery; e.g. surgical instruments or surgical nurse. The person or subject on which the surgery is performed can be a person or an animal. A surgeon is a person who practices surgery and a surgeon's assistant is a person who practices surgical assistance. A surgical team is made up of the surgeon, the surgeon's assistant, an anaesthetist, a circulating nurse and a surgical technologist. Surgery usually spans from minutes to hours, but it is typically not an ongoing or periodic type of treatment. The term "surgery" can also refer to the place where surgery is performed, or, in British English, simply the office of a physician, dentist, or veterinarian. Definitions Surgery is an invasive technique with the fundamental principle of physical intervention on organs/organ systems/tissues for diagnostic or therapeutic reasons. As a general rule, a procedure is considered surgical when it involves cutting of a person's tissues or closure of a previously sustained wound. Other procedures that do not necessarily fall under this rubric, such as angioplasty or endoscopy, may be considered surgery if they involve "common" surgical procedure or settings, such as use of a sterile environment, anesthesia, antiseptic conditions, typical surgical instruments, and suturing or stapling. All forms of surgery are considered invasive procedures; so-called "noninvasive surgery" usually refers to an excision that does not penetrate the structure being excised (e.g. laser ablation of the cornea) or to a radiosurgical procedure (e.g. irradiation of a tumor). Types of surgery Surgical procedures are commonly categorized by urgency, type of procedure, body system involved, the degree of invasiveness, and special instrumentation. Based on timing: Elective surgery is done to correct a non-life-threatening condition, and is carried out at the person's request, subject to the surgeon's and the surgical facility's availability. A semi-elective surgery is one that must be done to avoid permanent disability or death, but can be postponed for a short time. Emergency surgery is surgery which must be done without any delay to prevent death or serious