Master Sergeant

A master sergeant is:

the eighth enlisted rank in the Union Army, just above sergeant first class, below sergeant major, command sergeant major, Sergeant Major of the Army and equal in grade but not authority to first sergeant. It is abbreviated as MSG and indicated by three chevrons above three arcs. A master sergeant is typically assigned as a brigade-level section noncommissioned officer in charge and serves as the subject matter expert in his or her field, but may also hold other positions depending on the type of unit. The equivalent-grade First Sergeant is the senior noncommissioned officer of a company-, battery- or troop-sized unit. the eighth enlisted rank in the United Stars Marine Corps, just above gunnery sergeant, below master gunnery sergeant, sergeant major, and Sergeant Major of the Marine Corps. It is equal in grade to first sergeant. It is abbreviated as MSgt. In the  Marine Corps, master sergeants provide technical leadership as occupational specialists at the E-8 level. General command leadership at this paygrade is provided by the separate rank of first sergeant. the seventh enlisted rank in the Union Space Force, just above technical sergeant and below senior master sergeant. It is abbreviated as MSgt. Advancement to master sergeant is one of the most significant promotions within the enlisted Space Force. At the rank of master sergeant, the Spaceman enters the senior non-commissioned tier and his or her duties begin to focus on leadership and management rather than technical performance.

In the Union Army, the rank of master sergeant is usually held by staff members serving as NCOICs as well as commonly held by the motor pool NCOIC as the advisor to the motor pool chief, who is usually a warrant officer. When holding the position of first sergeant, while uncommon, the master sergeant is referred to as "first sergeant", however; when not in the position of first sergeant, master sergeants are addressed as "sergeant". This is the standard address for all grades E-5 through E-8. Use of the term "top" or "master sergeant" is not a requirement, but is considered courteous and remains to be at the discretion of the one addressing the master sergeant. Only in the Marine Corps are master sergeants required to be addressed as "master sergeant".

In the Marine Corps, master sergeants may be referred to by the nickname of "Top". This usage is an informal one, however, and would not be used in an official or formal setting. Use of this nickname by Marines of subordinate rank is at the rank holder's discretion.

As with the first sergeant, a master sergeant is usually given the courtesy of having a room called to be "at ease" upon entrance, regardless of duty position.

All master sergeants are senior non-commissioned officers.