What is meant when Romeo and Juliet are called star-crossed lovers?

The concept of fate functions as a central theme in Shakespeare's Romeo and Juliet. In the opening prologue of the play, the Chorus informs the audience that Romeo and Juliet are "Star ñ cross'd Lovers" (Prologue l.6). In other words, the Chorus states that Romeo and Juliet are governed by fate, a force often linked to the movements of the stars. Fate manifests itself in all the events surrounding the young lovers: the ancient and inexplicable feud between their families, the catastrophic series of mishaps which ruin Friar Lawrence's plans, and the tragic timing of Romeo's suicide and Juliet's awakening. The structure of the play itself rests upon the fate from which the two lovers cannot escape.