macron

例句：

1. 1. The macron is the smallest unit of measurement in the metric system.
   马克隆是公制系统中最小的计量单位。
2. 2. The macron is used to denote the beginning of a sentence or paragraph.
   马克隆用于表示句子或段落的开头。
3. 3. The macron is also used to indicate the end of a sentence or paragraph.
   马克隆还用于表示句子或段落的结束。