His letter was difficult to read because it had no punctuation.

punctuation 是名词，来自动词 punctuate（加标点），指"标点符号"或"标点法"。这个词由拉丁词根 punct（点）和后缀 -ation（表示动作或结果）组成，字面意思是"打点标记"，引申为"标点符号"。