An admiral is a high-ranking naval officer who commands a fleet or group of ships of a navy or holds an important naval post on shore. The rank of admiral is one of the highest ranks in some navies, including the United States Navy, the United States Coast Guard, and the Commonwealth nations). In the United States Navy, admiral is a four-star commissioned officer rank, which is equivalent to the rank of general in the other uniformed services). The term "admiral" comes from the Arabic term "amir-al-bahr," which means "commander of the seas". The word "admiral" has evolved from the Arabic term "amīral". The rank of admiral is above vice admiral and below admiral of the fleet or fleet admiral). The term "full admiral" is used to refer to a four-star admiral, and informally, "four-star admiral" or "O-10" is used to distinguish a four-star admiral from other ranks).