Different airlines provide the definition of passenger type differently. however,there are basically three types of passengers as follow
1) Infant passenger is a lap-help passenger who has not reached his or her second birthday at the time of travel. AN infant passenger must be accompanied by the parent or the legal guardian. Domestically infants travel free but for international travel, the fare is approximately 10% of the applicable adult's fare excluding taxed, fees and surcharges.
2)Child passenger is a passenger who is over two years of age at the time of travel. Child passenger must occupy a seat and be accompanied by an adult passenger. Depending on the routes and airlines, the child fare is around 50-75% of the applicable adult's fare excluding taxes, fees and surcharges. Some airlines accommodate a child of a certain age to travel alone. He or she must be booked as an unaccompanied minor (UMNR). UMNR fees will be applied to the booking.
3)Adult passenger is a passenger who has reached his or her 12 birthday at the time of travel.