在英语中，"four years old" 可以表示 "four years of age"，所以可以说 "four years old and happy" 来表示 "四岁快乐"。这个表达方式源于英语中表示年龄的常用说法。
下面是一些例句和中文翻译：
My son is four years old and happy. 我儿子四岁快乐。
My daughter just turned four and she is so happy. 我女儿刚满四岁，她很开心。
I can't bepeve my pttle girl is already four years old and so grown up. 我简直不敢相信我的小女孩已经四岁了，而且长大了这么多。
下面是一些例句和中文翻译：
My son is four years old and happy. 我儿子四岁快乐。
My daughter just turned four and she is so happy. 我女儿刚满四岁，她很开心。
I can't bepeve my pttle girl is already four years old and so grown up. 我简直不敢相信我的小女孩已经四岁了，而且长大了这么多。