fiancée
A person you are engaged to marry.
A fiancée (if she's a woman) or fiancé (if he's a man) is the person someone is engaged to marry. When two people decide they want to get married, they become engaged, and during the time between the engagement and the wedding, they call each other fiancé or fiancée.
This French word captures a special in-between stage: more committed than boyfriend and girlfriend, but not yet husband and wife. When someone introduces “my fiancée,” they're saying “this is the person I've promised to marry.” The engagement period gives couples time to plan their wedding and prepare for married life together.
You might hear someone say, “She introduced her fiancé to her grandparents,” or “His fiancée helped him pick out a new suit for the wedding.” The engagement usually begins when one person proposes marriage and the other accepts, and it may be marked by an engagement ring. Some couples are engaged for a few months, others for a year or more, depending on how much time they need to plan their wedding and feel ready for marriage.