Being twenty years old; the age of twenty (often read はたち), commonly associated with becoming an adult in Japan.
彼女は今年、はたちになる。
She will turn twenty this year.
二十歳（20歳）になると、法律上は成人とみなされる。
At age twenty (20), one is legally regarded as an adult.
成人式は多くの人が二十歳ではたちを祝う行事だ。
Coming-of-age ceremonies are events where many people celebrate being twenty.
An archaic or literary form meaning 'twenty' (the number 20); seldom used in modern everyday language.
古い文書では『廿』という字で二十を表すことがある。
In old documents the character '廿' is sometimes used to represent twenty.