愁苦的表情用英语可以表示为"a sorrowful expression"或"a mournful expression"。

这两个词都源于拉丁文，"sorrow"来自拉丁文的"sorrow"，意思是悲伤、悲痛，"mourn"来自拉丁文的"moerere"，意思是哀伤、哀悼。

下面是一些使用"a sorrowful expression"或"a mournful expression"的例句：

He looked at me with a sorrowful expression on his face.
他用愁苦的表情看着我。

She gazed at the painting with a mournful expression.
她用哀伤的表情凝视着这幅画。

His face was a mask of sorrow, his eyes filled with tears.
他的脸上带着愁苦的表情，眼里盈满了眼泪。

The news of her husband's death left her with a mournful expression.
她丈夫的死讯让她的表情变得哀伤。