Sergeant (rank)
Sergeant (abbreviated to Sgt and capitalised when used as a named person's title) is a rank in many uniformed organizations, principally military and policing forces. Its origin is the Latin serviens, "one who serves", through the French term sergent.
The term "sergeant" refers to a non-commissioned officer placed above the rank of a corporal and a police officer immediately below a lieutenant. In most armies the rank of sergeant corresponds to command of a squad (or section). In Commonwealth armies, it is a more senior rank, corresponding roughly to a platoon second-in-command. In the United States Army, sergeant is a more junior rank corresponding to a four-soldier fireteam leader.
More senior non-commissioned ranks are often variations on sergeant, for example staff sergeant, first sergeant and sergeant major.
Many countries use sergeant rank, whether in English or using a cognate with the same origin in another language. The equivalent rank in Arab armies is raqeeb, meaning "overseer" or "watcher".
In medieval European usage, a sergeant was simply any attendant or officer with a protective duty. Any medieval knight or military order of knighthood might have "sergeants-at-arms", meaning servants able to fight if needed. The etymology of the term is from Anglo-French sergant, serjant "servant, valet, court official, soldier", from Middle Latin servientem "servant, vassal, soldier".
Later, a "soldier sergeant" was a man of what would now be thought of as the "middle class", fulfilling a slightly junior role to the knight in the medieval hierarchy. Sergeants could fight either as heavy to light cavalry, or as well trained professional infantry, either spearmen or crossbowmen. Most notable medieval mercenaries fell into the "sergeant" class, such as Flemish crossbowmen and spearmen, who were seen as reliable quality troops. The sergeant class was deemed to be 'worth half of a knight' in military value.
...
Wikipedia