对某人保持沉默用英语怎么说

"To keep silence about someone" 在英文中可以用 "to keep quiet about someone" 或 "to keep mum about someone" 表示。

"to keep quiet" 是 "保持安静" 的意思，而 "mum" 是 "沉默" 的意思。这两种用法都可以表示 "对某人保持沉默" 的意思。

举例：
"I promised to keep quiet about our secret plan." (我答应过不会提起我们的秘密计划)
"He asked me to keep mum about his financial troubles." (他让我不要提他的财务困境)