The pair admitted that their three-year-old marriage was going through "a difficult time."
那对夫妇承认他们3年的婚姻正在经历一个困难时期。
《柯林斯英汉双解大词典》
2
Actually, the three-year-old dog is a good "shopkeeper".
实际上，这只三岁的狗是个很好的“店主”。
3
A three-year-old might need help in understanding that other children feel pain just as he does, and that hitting a playmate over the head with a heavy toy requires an apology.