This was cut and pasted from the Navy's own site (see Hoppi's discussion on this groups page).
The word "rate" is used in two ways within the structure. First, rate is a paygrade. Enlisted navy personnel do not have rank, only naval officers. Second, rate is an abbreviation that contains both the rating and the paygrade abbreviations. For example, a Boatswain's Mate has the rating abbreviation BM, and if the person is a Petty Officer Second Class which is a "2" abbreviation, then the person's rate would be BM2 (BM is the rating and the 2 is Petty Officer Second Class paygrade E5). The paygrade abbreviation is always added right after the rating abbreviation. The rates (Paygrades) are as followed:
Paygrades E1 through E3 can also have a rating abbreviation preceding their paygrade symbol IF they are graduates of Class "A" schools.
SR, Seaman Recruit E-1
SA, Seaman Apprentice E-2
SN, Seaman E-3
Once they finish A-School, they will be addressed by their rate first, then their paygrade.
Using the example of a Sailor who is an IT (Information Technologist), it would read as follows:
and so on.....