Synchronic and diachronic are a couple of important conception.

共时和历时是一对重要的概念。

The synchronic comparison should be combined with the diachronic one.

是结合共时性比较和历时性比较。

Diachronic or historical arrangement or analysis, especially of language.

历时，分析：历时的或历史的整理或分析，尤指语言。

And it lays stress on synchronic analyses as well as diachronic comparison.

主要着眼于共时分析，也注意历时比较。

Diachronic: study of a language is carried through the course of its history.

历时：在语言的历史过程中研究语言。