- 一级市场 yījíshìchǎng primary marketThe financial market where new securities like stocks and bonds are issued for the first time; distinct from the secondary market
- 第一级 dìyījí first levelthe first or highest level in a hierarchy or ranking
- 一级方程式 yījífāngchéngshì Formula OneFormula One; the highest class of international racing for open-wheel single-seater formula racing cars
- 一级棒 yījíbàng first-rateexcellent; awesome; first-rate. Originally a loanword from the Japanese word [[一番|一番|yi1 fan1]] (ichiban).
- 国家一级保护 guójiāyījíbǎohù state-protected grade oneSpecifically refers to plant and animal species that are granted the highest level of legal protection by the national government.
- 第一级产业 dìyījíchǎnyè primary industrythe sector of an economy making direct use of natural resources, including agriculture, forestry, fishing, and mining
- 一级士官 yījíshìguān corporal or sergeanta rank of non-commissioned officer in the Chinese People's Liberation Army; corporal or sergeant
- 一级头 yījítóu first stageThe first stage of a scuba diving regulator, which reduces high-pressure air from the tank to an intermediate pressure.