- 二级军士 èrjíjūnshì Master Sergeanta non-commissioned officer rank in the Chinese People's Liberation Army, typically referring to the second-highest level of non-commissioned officers
- 二级士官 èrjíshìguān sergeant
- 二级头 èrjítóu second stagesecond stage (scuba diving)
- 二级头呼吸器 èrjítóuhūxīqì regulator(scuba diving) regulator; demand valve
- 备用二级头呼吸器 bèiyòng'èrjítóuhūxīqì octopusa backup regulator used in scuba diving, often referred to as an octopus
