There are several different Sergeant ranks. The most basic Sergeant rank is E5 in the Army and Marine Corps. It is only E4 in the Air Force.
Master Sergeant in the Army is pay grade E8. First Sergeant is the other Army E8 rank.
E6 is the pay grade.
In the Army and Marines, it's First Sergeant, which are both pay grade E8. In the Air Force, Master Sergeant is pay grade E7, but First Sergeant isn't a separate rank, although it is denoted with a diamond similar to what it used on Army and Marine Corps First Sergeant rank insignia. In the Air Force, the designated First Sergeant can be pay grades E7 through E9.
In the Army and Marines, it's First Sergeant, which are both pay grade E8. In the Air Force, Master Sergeant is pay grade E7, but First Sergeant isn't a separate rank, although it is denoted with a diamond similar to what it used on Army and Marine Corps First Sergeant rank insignia. In the Air Force, the designated First Sergeant can be pay grades E7 through E9.
The US Army has a sergeant 1st class, it is the pay grade of E7, ranked above a Staff Sergeant and below a Master Sergeant.
Gunnery Sergeant is pay grade E7, and the equivalent Army rank is Sergeant First Class.
Sergeant First Class is pay grade E7. In the Army, the next pay grade - E8 - has two ranks within it - Master Sergeant, and First Sergeant. The difference being that a First Sergeant is a company's senior NCO, whereas Master Sergeant tends to denote NCOs holding staff positions.
Yes. Staff Sergeant is pay grade E6 in both the US Army and US Marine Corps (it's pay grade E5 in the Air Force).
A sergeant is an enlisted soldier higher in rank than a corporal or private, lower than such ranks as staff sergeant and first sergeant. In the U.S. Army a sergeant has pay grade E-5 and wears three stripes.
SSGT is a military rank in the US Air Force that means Staff Sergeant. In the US Air Force, it is used to signify an individual in the pay grade of E-5. In the Army and Marine Corp, the same name and abbreviation are used, but in this case, they signify someone in the pay grade of E-6.
In the US Army, the next rank above Staff Sergeant would be Sergeant First Class, followed by Master Sergeant and First Sergeant (both grade E8), then by Sergeant Major and Command Sergeant Major (both grade E9). Sergeant Major of the Army is the seniormost noncommissioned officer rank in the US Army. In the US Marine Corps, the next rank above Staff Sergeant (E6) would be Gunnery Sergeant (E7), followed by Master Sergeant and First Sergeant (E8), Master Gunnery Sergeant and Sergeant Major (E9), then Sergeant Major of the Marine Corps. Unlike other military branches of the US Armed Forces, where Staff Sergeant is pay grade E6, Staff Sergeant in the Air Force is pay grade E5 - equivalent to a Sergeant in the Army or Marine Corps. It is followed by Technical Sergeant (E6), Master Sergeant (E7), Senior Master Sergeant (E8), Chief Master Sergeant and Command Chief Master Sergeant (E9), and, finally, Chief Master Sergeant of the Air Force, who - like the Sergeant Major of the Army and the Sergeant Major of the Marine Corps - is the most senior noncommissioned officer in the entire branch. The British, Commonwealth, and some European forces end their enlisted ranks at Staff Sergeant (or equivalent), and rate enlisted personnel senior to Staff/Colour Sergeants as Warrant Officers.
There are three ranks within the pay grade of E9 - Sergeant Major, Command Sergeant Major, and Sergeant Major of the Army. There is only one Sergeant Major of the Army.