When i am middle aged.为什么不用middle age呢?

When i am middle aged.为什么不用middle age呢? middle-age和middle-aged 一样吗 middle-aged什么意思 a middle-aged high middle age 哪个时期呢 i know the middle -aged woman____ i saw yesterday. I am not comfortably middle class;I am uncomfortably middle I am a middle school I was in junior middle school when I was sat the age of 13 他 school-age ,middle-aged 都是形容词一个加的 一个不加 I am going to be a teacher when I ----middle school. i am a middle school's(.)