- 第二次 dì'èrcì second timethe second time; second; number two
- 二次元 èrcìyuán ACG worldthe fictional worlds of anime, comics, and games (Japanese: nijigen)
- 二次大战 èrcì Dàzhàn World War II
- 二次函数 èrcìhánshù quadratic function
- 二次方 èrcìfāng squaresquare (a number multiplied by itself)
- 二次曲线 èrcìqūxiàn conica quadratic curve or conic section in geometry, such as a circle, ellipse, parabola, or hyperbola
- 二次型 èrcìxíng quadratic formquadratic form (math.)
- 二次曲面 èrcìqūmiàn quadric surfacequadric surface (geometry)
- 一元二次 yīyuán'èrcì quadraticin mathematics, relating to an equation involving one variable raised to the second power and no higher power.
- 第二次汉字简化方案 Dì'èr Cì Hànzì Jiǎnhuà Fāng'àn Second SimplificationThe second round of simplified Chinese characters proposed in 1977 and retracted in 1986, often abbreviated as [[二简|二簡|Er4 jian3]].
- 二次世界大战 èrcì Shìjiè Dàzhàn World War IIWorld War Two
- 二次多项式 èrcìduōxiàngshì quadratic polynomial(math.) quadratic polynomial
- 二次方程 èrcìfāngchéng quadratic equation
- 二次曲 èrcìqū conica plane curve defined by a second-degree algebraic equation, such as an ellipse, parabola, or hyperbola
- 二次革命 èrcì Gémìng Second RevolutionThe 1913 campaign of the provisional revolutionary government (led by Sun Yat-sen and the Guomindang) against Yuan Shikai and the Northern Warlords.
- 第二次世界大战 Dì'èr Cì Shìjiè Dàzhàn World War II
