The numeral eight (used as a counter word for eight items).
りんごを八つ買ってきてください。
Please buy eight apples.
箱の中には飴が八つ入っていた。
There were eight candies in the box.
An expression meaning 'eight years old' (a traditional way to state a child's age).
彼女は今年八つになる。
She will be eight years old this year.
昔話の主人公は八つの試練を乗り越える少年だ。
The hero of the folktale is a boy who overcomes eight trials.
In old timekeeping (pre-modern Japan), 'yattsu' (八つ) referred to roughly two o'clock (an old hour name).
古い文献には「八つに鐘が鳴った」と記されている。
The old document records that the bell rang at 'yattsu' (approximately two o'clock).