在完成写字之后，通常用英文表示为"finish writing"或者"complete writing"。

关于这个表达的来源，它来源于英文动词"finish"和"complete"。"Finish"的意思是"完成，结束"，"complete"的意思是"完成，结束，使完美"。在这里，"writing"是动词"finish"和"complete"的宾语，表示完成写字这个动作。

下面是一些英文例句以及它们的中文翻译：

I'm going to finish writing my essay tonight. (我今晚要写完我的文章。)
She completed writing the report last week. (她上周写完了报告。)
He always finishes writing his notes before class. (他总是在课前写完笔记。)
They finished writing the script for their play yesterday. (他们昨天写完了他们的剧本。)
She is going to complete writing her thesis next month. (她下个月要写完她的论文。)