In Romeo and Juliet, how does the ring that the nurse gives to Romeo represent a symbol?

The ring symbolises Juliet's overwhelming love and commitment to her first and only love, Romeo. It becomes more than just that, however, if one considers the turgid circumstances in which the two lovers find themselves. Their families have been lifelong enemies and the two lovers' current situation is that 'new mutiny' implies that old hatreds have flared up again, creating a disturbance in the beautiful and peaceful city of Verona.

What makes the situation much, much worse, though, is that Romeo has killed Juliet's cousin, Tybalt, in a duel when he avenged his friend, Mercutio, who had been killed by Tybalt. Prince Escalus has banished Romeo permanently, at the risk of the young lover forfeiting his life if he should be discovered in Verona.

The two lovers had, before these unfortunate developments, agreed to get married secretly with Friar Laurence conducting the ceremony. The nurse has just heard about the tragic events which have resulted in Romeo's sanction. She informs Juliet of the circumstances and the young girl is overwhelmingly distraught, so much so that she even considers committing suicide:

for Romeo is exiled:
He made you for a highway to my bed;
But I, a maid, die maiden-widowed.
Come, cords, come, nurse; I'll to my wedding-bed;
And death, not Romeo, take my maidenhead!

The nurse, however, tells her that she will speak to Romeo and urge him to secretly visit Juliet. It is then that Juliet presents her with the ring:

O, find him! give this ring to my true knight,
And bid him come to take his last farewell.

Against this backdrop, Juliet's token of love becomes almost sacrificial. She is saying, by presenting this ring to him, that she is prepared to risk everything, even her life, to be with him. She shows her unconditional allegiance to her love, Romeo, who should in fact, now more than ever, be her lifelong enemy.

When Romeo receives the ring, his spirits too, are revived for he had also felt suicidal. The ring to him symbolises some hope for happiness for he now knows that Juliet is still his and that, irrespective of the devastating circumstances they find themselves in, they will still have, and possibly be with, each other. He declares:

How well my comfort is revived by this!

He bids friar Laurence goodbye, saying:

But that a joy past joy calls out on me,
It were a grief, so brief to part with thee: Farewell.