A morpheme is the smallest grammatical unit in a language.

词素是语言中最小的语法单位。

A sentence is a grammatical unit.

一个句子是一个语法单位。

A morpheme is the minimal distinctive grammatical unit, and is the lowest unit grammatical hierarchy.

词素是最小的辨别语法单元，也是语法层次中最低级的单元。

Since sentence is usually regarded as the largest grammatical unit of a language, syntax has long been the center of grammatical study.

因为通常认为句子是语言中最大的语法单位，所以句法长期以来是语法研究的核心。

Traditionally, what is identified as aspect was subsumed under the term tense; aspect is viewed as a grammatical unit and is often confused with tense.

“体”传统上归属“时”，被认为是一个语法单位，经常与“时”混为一谈。