第40个生日的英文

Happy 40th Birthday.in some parts of the world (say, US) one can decorate it as "Black"--obviously it's moody for someone who's turning 40.

40岁生日：fortieth birthday,不是forty years' birthday. fortieth可以作为birthday的定语,意为第40个生日,也就是40岁生日. 而forty years可以说明人的年龄是多少,但并不用来修饰birthday,它只能当表语.