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Petty officer describes several enlisted ranks of non-commissioned officers in the United States Navy, ranging from E4 to E9, though conventionally used for E4 to E6.

The rates are as follows:

E4 Petty Officer Third Class
E5 Petty Officer Second Class
E6 Petty Officer First Class

Higher enlisted rankings wear a different uniform altogether, and are generally addressed as "Chief" rather than "Petty Officer".

E7 Chief Petty Officer
E8 Senior Chief Petty Officer
E9 Master Chief Petty Officer