Returning to the same word, phrase or construction, at the start of successive verses or sentences (anaphora) or throughout the text, to give rhythm, emphasis or insistence.
In Romeo and Juliet
My only love sprung from my only hate!
The adjective "only" returns on both sides of the sentence and brings love and hatred together. Repeated, it reinforces that there is no other love or other hatred possible for her, and that both come from the same source.
Act I: The brawl and the ball, Juliet
These violent delights have violent ends / And in their triumph die
Act II: The garden and the wedding, Friar Laurence
That 'banished,' that one word 'banished,' / Hath slain ten thousand Tybalts.
Act III: Mercutio, Tybalt, and the banishment, Juliet
Romeo, Romeo, Romeo! Here's drink. I drink to thee.
Act IV: The potion of apparent death, Juliet
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