用來代替「前面已提過」的同類可數名詞。單數用 one：The white skirt looks more beautiful than the brown one. （這條白色裙子看起來比那條咖啡色的美。）one ／ ones 和 it ／ they 的區別在於it（單數）／ they（複數）用來代替前面提過的「同一」名詞，如： My dad gave me a bike as a birthday present. I ride it to school every day. （我爸爸送我一部腳踏車當生日禮物。我每天騎它去上學。）