When it comes to greeting Soldiers E5 and above, does "Sergeant" suffice, or should you always use their full title?

I'm glad someone started this discussion. Regardless of what the regulation says, I think it's disrespectful to not address a Soldier by the entire rank. As a prior service Marine, if you called a GySgt a Sergeant, you were essentially demoting them. The Army, in my opinion, should not call a rank higher than E5 sergeant. I always address an NCO by their rank because at the end of the day, they earned it and they deserve to be called that rank. You wouldn't call a CPT or MAJ a lieutenant so why do that on the enlisted side.

it was appropriate and proper to address me as "sergeant". since I was an E-5, that was my title.

There is only one Sergeant in the Army and Marine Corp. Imagine walking up to the Division CSM and saying "Hi Sergeant how are you today". It would like be an educational moment!

E-5 to E-8 Master Sergeant, Sergeant is the recognized greeting.
E-8 1SG (First Sergeant), Personally I didn't mind if the Soldiers called me (Top) or (First Shirt) some folks have been known to melt down over both, but they knew I was running shit and those titles have tradition and history to them. (know the person you're addressing before calling a 1SG anything other than First Sergeant, some folks need their egos stroked)
E-9 Sergeant Major for both (SGM) and (CSM).
E-1 to E-3 Private, is appropriate but I always recognized the PFCs as (PFC).
E-4 Specialists its (Specialist) E-4 Corporal (Corporal) It took me years to get used to calling specialists , (Specialist) because we used to have SPC-4 to SPC-7 when I came in, so an E-4 Specialist was commonly called a (Spec-4) in conversation and their title was (specialist) for all grades as title of address .

I generally call them by their full rank.

Private - Private First Class, Private.
Specialist - Specialist
Corporal - Corporal
Sergeant - Sergeant First Class, Sergeant

Master Sergeant - Master Sergeant, You can get away with calling them Sergeant, but call them MSG it's more respectful of their time and grade. You might catch shit around other Soldiers if you call Master Sergeant just Sergeant too.

First Sergeant - First Sergeant, Top
Sergeant Major - Sergeant Major
Command Sergeant Major - Usually just Sergeant Major but some instances I've seen CSM used, usually when a Private is scared out of his mind.

Warrant Officer 1 - Sir, could use Mr. if you outranked them.
Chief Warrant Officer 2 - 5, Sir or Chief

'Seaman'/'Airman'/'Fireman' for E3 and below is also appropriate.

Don't forget about the poor Corporal trying to figure out life as an NCO.

NCO's in the Army are addressed as Corporal, Sergeant (for SSG, SFC, or MSG), First Sergeant, or Sergeant Major.

In the Marine Corps they are addressed rank specific.

Learned something new about the Navy! Thanks! Dave

LTJG (Join to see), My opinion is calling a SSGT Staff Sergeant, an SFC a Sergeant First Class, etc. I think it's proper to call a Sergeant by their rank title. Would you call a LT. Colonel a Colonel?