What is the meaning of the abbreviation of the naval rank 'MM'?

Answer 1

In the United States Navy, enlisted sailors use their "rate" and "rank" together as one abbreviation. The rate, or job, is represented by either a 2- or 3-letter combination. The rank is represented by either letters or numbers, depending on the rank. For example, and to answer the question, MM stands for Machinist's Mate. There are others such as BM (Boatswain's Mate), QM (Quartermaster) and OS (Operations Specialist). Any rate that uses three letters is a sub-rating, e.g., ABF and ABH. Both ratings are Aviation Boatswain's Mates; however, ABF is the sub-specialty of Fuels and ABH is the sub-specialty of Handling. Another example of this is GSM and GSE. Both are Gas Turbine Systems Technicians, with the GSM specializing in Mechanical and the GSE specializing is Electrical. The rank of the sailor is indicated by the use of either numbers or letters. A Petty Officer will be indicated by either a 1, 2 or 3 (First, Second, and Third class Petty Officer). A Chief Petty Officer is indicated by a C, a Senior Chief Petty Officer by CS, and a Master Chief Petty Officer by CM. Also, for sailors that are E-3 and below, the rank indication changes slightly depending on which of the five rating groups they are part of. The five groupings are Seaman, Airman, Fireman, Constructionman, or Hospitalman. They are abbreviated by S, A, F, C, and H respectively. Then, there will be a second letter that indicates the rank. Time for some examples... A boatswain's mate is in the seaman grouping. Therefore, an E-3 in that rating would be abbreviated as BMSN (Boatswain's Mate Seaman), an E-5 would be BM2 (Boatswain's Mate Second Class) and an E-7 would be BMC (Chief Boatswain's Mate). More information can be found by researching naval ratings on wikipedia.com.