- 周期表 zhōuqībiǎo periodic tableperiodic table of the chemical elements; a chart of elements arranged by increasing atomic number so that those with similar properties fall into the same column
- 双周期性 shuāngzhōuqīxìng double periodicity(math.) double periodicity
- 周期定律 zhōuqīdìnglǜ periodic lawscientific law stating that the physical and chemical properties of elements recur in a systematic and predictable way when the elements are arranged in order of increasing atomic number
- 周期律 zhōuqīlǜ periodic lawThe general law that things or objects move or change in regular cycles.
- 周期数 zhōuqīshù periodic number
- 周期系 zhōuqīxì periodic systemthe periodic system of chemical elements; periodicity in chemistry
- 周期解 zhōuqījiě periodic solutiona periodic solution, especially within the context of mathematics
- 生命周期 shēngmìngzhōuqī life cycleThe series of stages through which a living thing passes from its beginning until its death; life cycle.
- 元素周期表 yuánsùzhōuqībiǎo periodic tablethe periodic table of the chemical elements
- 经济周期 jīngjìzhōuqī economic cyclethe periodic fluctuations in economic activity, including periods of growth and recession