Fiancée

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

Frequently when they were very young, Vulcans were bonded with someone whom they might eventually have married. 

Anne Nored was Carter Winston's fiancée prior to his death. 

Ferengi entered into a contract in which the male "leased" the female from her father. Typically, the contract was valid for only a few years. The male had the option of extending the contract if he showed strong feelings for the female he was married to. 

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

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