tender age
A youthful age. I'm not surprised to hear that he was doing science experiments at such a tender age—he's a child genius! I experienced my first true heartbreak at the tender age of 18.
tender age of
the young age of... She left home at the tender age of 17 and got married to a rock singer.
tender age
A young age, as in It's a great advantage to learn languages at a tender age. [Early 1300s]