let: may imply a positive giving of permission but more often implies failure to prevent either through inadvertence and negligence or through lack of power or effective authority: the goalie ~ the ball get by her.


allow: implies little more than a forbearing to prohibit or to exert this power: a teacher who ~s her pupils to do as they like.


permit: implies express willingness or acquiescence: the park ~s powerboats on the lake.


suffer: can be close to allow or may distinctively imply indifference or reluctance: ~ed themselves to be photographed.  (indifferent无所谓、中立，reluctance不情愿)


leave: stresses the implication of noninterference in letting or allowing or permitting and can suggest the departure of the person who might interfere: ~ them to resolve the matter among themselves.


let允许让: 可指明确允许，但更多表示疏忽失误无力而未能阻止，allow允许: 仅表示出于克制而不去禁止，permit允许: 指明确愿意或指默许，suffer忍受: 和allow接近，或表示选择忍受，leave留给不干预: 表示本可干预的人不干预


记忆方法: 1) 首字母ALL PS想成pass全通过<==允许     "允"和"许"的意思相同，都表示"答应认可"。另外，这两个字分别还有第二个意思。 允的另一个意思也是本意，表示"诚信": "允，信也"，如允当公允；许的另一个意思是"数量上接近"，如些许少许稍许许多许久八时许庭院深深深几许

         2) 允许的意思是不禁止阻止mean not to forbid or prevent.首字母ALL PS想成pass全通过<==允许