Although this word consists of one kanji that is all alone, it doesn't share its meaning with the parent kanji. The meanings are similar in a way, though. This word means years old or age. With more years comes more genius, right? That's why this word means "years old" and not "genius," like the parent kanji.

You can stick this word onto numbers to say how old someone is!

Special note for all of you advanced learners out there. When discussing age, 〜歳 is the original and correct kanji to use. Because 〜才 is easier to write and has the same reading, it became mainstream. You'll see it used in writing today, especially in elementary schools. In formal writing though, you'll always want to use 〜歳, which you'll learn later on.