What differentiates a single entry from a multiple-entry visa?
This depends on the reciprocal treaties governing visa issuance for each nationality. A visa may allow the traveler to enter at various times or it may permit only one entry before its expiration. Restrictions of time (expiration date of the visa), the nationality of the traveler, or restrictions placed on the total number of days permitted in country during any year govern the number of times that a multiple-entry visa may be used. A single-entry visa may only be used for one entry for the specific purpose for which it was granted.