Years Old
Year, Time
You have to stop keeping canines which are small once you reach a certain number of years old. You'll be hitting that age limit this year, which means your time with your small canine will end and you'll have to grow up and get a bigger one.
さい, せい
とし, とせ
None
Remember the vocab word 〜才 which also meant "years old"? Well, this has the same reading: さい.