"祝姥爷生日快乐" 用英语可以说成 "Happy birthday to grandfather" 。
"grandfather" 是英文中表示 "祖父" 的词，而 "happy birthday" 则是祝福生日快乐的常用语。
一些例句：
"Happy birthday, grandfather! Wishing you all the best on your special day."
"Warm wishes to you on your birthday, grandfather. Have a great day!"
"Sending lots of love and birthday wishes to the best grandfather in the world. Happy birthday!"
这些例句中，"Happy birthday, grandfather!" 是最简短的祝福语；"Wishing you all the best on your special day." 则是祝福对方度过美好的一天；"Have a great day!" 是祝福对方度过愉快的一天；"Sending lots of love and birthday wishes" 是表达爱意和祝福的话语。