1 有 than时,比较级的前面永远没有the :
She is taller than her sister。
She is a taller girl than her sister
Who is taller , Mary or her sister ?
2 有the时,永远是 the taller of - -或者the taller +名词单数 of -- - :
Mary is the taller of the two girls.
Mary is the taller girl of the two.