Permission, leave, sufferance denote the sanction which enables one to do something that requires the consent of those in authority.
Permission is the ordinary term except in some conventional phrases; it commonly implies the power or authority to grant or to refuse what is asked.
Leave differs very little from permission. It occurs chiefly in conventionally courteous phrases such as "by your leave ," "to ask leave, " and "give me leave, " but it may be used elsewhere in place of permission.
In military, naval, and, some official use the term implies official permission to absent oneself from one's duties or from one's station for a fixed period of time, or the furlough or absence so permitted.
Sufferance usually implies a neglect or refusal to forbid and therefore suggests either a tacit permission withdrawable on cause or, more often, merely allowing a person to be present or to do something.