Petty officer
Petty officer was a subordinate non-commissioned officer rank used primarily by Earth service organizations. 

An United States Navy petty officer, serving as an electronics technician aboard the aircraft carrier , was on duty when the ship was "raided" by a "Russkie" named Pavel Chekov in 1986. ()

During the late 23rd century, Starfleet petty officers were ranked either petty officer, 1st class or petty officer, 2nd class, and displayed silver octagon-shaped insignia with two different textures to denote class. (–) 

Starfleet still used this rank in the late 24th century. ()

List of petty officers 
 Bekka (1st class) 
  (Operations division, Deep Space 9)
 Chanak (2nd class & 1st class) 
 Donas (1st class) 
 Marva (1st class) 
 Moonsafi (1st class) 
 Pashtor (1st class) 
  (1st class) 
 Salak (1st class) 
 Samno (1st class) 
 Smalla (1st class) 
 Stoyra (2nd class)
 Strath (1st class) 
 Tamaron (1st class) 
 Zanatos (1st class)
 Zorath (2nd class)

Appendices

See also
 Starfleet enlisted personnel

Background information 

The term petty officer is never used in the Star Trek films, but comes from Robert Fletcher's costuming production notes. (p. 9) The It's A Wrap! sale and auction featured numerous lots containing 1st class and 2nd class insignia pins. 

The grades of petty officer 1st class, chief petty officer, senior chief petty officer, master chief petty officer 2nd class, and master chief petty officer (but not petty officer 2nd class) were used in . , lists petty officer 2nd class, but skips petty officer 1st class, and displays a chief petty officer insignia mislabeled "petty officer."

A triangle insignia used in  was not identified to a rank, through It's a Wrap! sale and auction has described it as the  petty officer insignia. 

As Starfleet ranks in Star Trek are mostly based on the ranking systems of "real world" militaries, the following may be true: the rank of "petty officer", which is the lowest to be categorized as "noncom", would be senior to a crewman and subordinate to a chief petty officer. The requirements to be a rated a yeoman (as was the case with Samno) or a specialist would fall into the category of a "petty officer". In comparison to infantry ranking systems, this rank was approximately equivalent to the grade of sergeant.

External link 
 
 
 

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Military ranks