我生日用英文怎么说

"birthday"是英语中表示"生日"的词。这个词来源于中世纪英语"birþ-dæg"，在古英语中意为"生之日"，由两个词组成："birþ"意为"生"，"dæg"意为"日"。

例句：

"Today is my birthday." (今天是我的生日。)
"Happy birthday to you!" (祝你生日快乐！)
"I'm having a birthday party tonight." (今晚我要举办生日派对。)
"He gave me a birthday present." (他给了我一件生日礼物。)