A soldier is a person who is a member of an army. A soldier can be a conscripted or volunteer enlisted person, a non-commissioned officer, or an officer. Etymology The word soldier derives from the Middle English word , from Old French or , meaning mercenary, from , meaning shilling's worth or wage, from or , shilling. The word is also related to the Medieval Latin , meaning soldier (literally, "one having pay"). These words ultimately derive from the Late Latin word , referring to an Ancient Roman coin used in the Byzantine Empire. Occupational and other designations In most armies, the word "soldier" has a general meaning that refers to all members of any army, distinct from more specialized military occupations that require different areas of knowledge and skill sets. "Soldiers" may be referred to by titles, names, nicknames, or acronyms that reflect an individual's military occupation specialty arm, service, or branch of military employment, their type of unit, or operational employment or technical use such as: trooper, tanker (a member of tank crew), commando, dragoon, infantryman, guardsman, artilleryman, paratrooper, grenadier, ranger, sniper, engineer, sapper, craftsman, signaller, medic, or gunner, among other terms. Some of these designations or their etymological origins have existed in the English language for centuries, while others are relatively recent, reflecting changes in technology, increased division of labor, or other factors. In the United States Army, a soldier's military job is designated as a Military Occupational Specialty (MOS), which includes a very wide array of MOS Branches and sub-specialties. One example of a nickname for a soldier in a specific occupation is the term "red caps" to refer to military police personnel in the British Army because of the colour of their headgear. Infantry are sometimes called "grunts" in the United States Army (as the well as in the U.S. Marine Corps) or "squaddies" (in the British Army). U.S. Army artillery crews, or "gunners," are sometimes referred to as "redlegs", from the service branch colour for artillery. U.S. soldiers are often called "G.I.s" (short for the term "General Issue"). Such terms may be associated with particular wars or historical eras. "G.I." came into common use during World War II and after, but prior to and during World War I especially, American soldiers were called "Doughboys," while British infantry troops were often referred to as "Tommies" (short for the archetypal soldier "Tommy Atkins") and French infantry