admission基本含义
n.(机构、组织等的) 准许加入，加入权，进入权；(尤指对过错、罪行的') 承认，招认，招供；入场费；门票费;
[例句]Students apply for admission to a particular college.
学生们申请上某所大学。
复数：admissions
admittance含义
n.(建筑物、机构等的) 进入权，进入;
[例句]We had not been able to gain admittance to the flat.
我们未能获准进入公寓。