Fiancée

A fiancée is a person to whom another person will be wedded at a later date. Typically, after a lengthy courtship, a Human male suitor asks a female to become his fiancée, often with an offer of a diamond ring. 

Frequently when they are very young, Vulcans are bonded with someone whom they may eventually marry. 

Ferengi enter into a contract in which the male "leases" the female from her father. Typically, the contract is valid for only a few years. The male has the option of extending the contract if he shows strong feelings for the female he is married to. 

Betazoid children are sometimes bonded to the person they might marry in adulthood. 

Bajorans are often betrothed at a young age, with the girl signifying this status with a bracelet.