[tlhIngan Hol] expressing age expressing "year old" expressing "years old"

I can't understand why we can't just say {cha'maH DIS loD} for "twenty year old man". -- Dana'an https://sacredtextsinklingon.wordpress.com/ Ζεὺς ἦν, Ζεὺς ἐστίν, Ζεὺς ἔσσεται· ὦ μεγάλε Ζεῦ