What are secrets in Romeo and Juliet?

There are several examples of characters keeping secrets in Shakespeare's Romeo and Juliet. All of the secrets, however, are well known to the audience. Shakespeare uses dramatic irony throughout the play and while some characters may be unaware of what is really going on, the audience knows the whole story.

In the opening scene, Romeo has a secret which is causing him to be depressed and to spend long stretches of his day walking...

There are several examples of characters keeping secrets in Shakespeare's Romeo and Juliet. All of the secrets, however, are well known to the audience. Shakespeare uses dramatic irony throughout the play and while some characters may be unaware of what is really going on, the audience knows the whole story.

In the opening scene, Romeo has a secret which is causing him to be depressed and to spend long stretches of his day walking alone or in the darkness of his room. Lord Montague asks Benvolio to discover what secret is bothering his son. Romeo eventually confesses to Benvolio that he loves a woman who does not reciprocate that love. He says,

Well in that hit you miss. She’ll not be hit
With Cupid’s arrow. She hath Dian’s wit,
And, in strong proof of chastity well armed,
From love’s weak childish bow she lives uncharmed.

The main secret in the play, however, is that Romeo and Juliet, offspring of families involved in a bitter feud, are in love and get married at the end of Act II. The only other characters who know of their love until the final scene are the Nurse and Friar Lawrence. Their secret causes chaos, beginning in Act III when Tybalt confronts Romeo. Tybalt does not know Romeo has just married his cousin. Romeo responds to Tybalt, implying there is a secret. He says in Scene 1,

Tybalt, the reason that I have to love thee
Doth much excuse the appertaining rage
To such a greeting. Villain am I none.
Therefore farewell. I see thou knowest me not.

Because of the secret, Mercutio is killed and Romeo kills Tybalt in revenge.

More chaos ensues when Lord Capulet seeks to marry his daughter to the wealthy Count Paris. Because he doesn't know the secret he can't understand Juliet's refusal and berates her and threatens to disown her. Capulet says in Act III, Scene 5,

An you be mine, I’ll give you to my friend.
An you be not, hang, beg, starve, die in the streets,
For, by my soul, I’ll ne’er acknowledge thee,
Nor what is mine shall never do thee good.
Trust to ’t; bethink you. I’ll not be forsworn.

Looking for a solution, Juliet seeks advice from the Friar, and the priest gives her a sleeping potion which will allow her to fake her death and avoid marrying Paris. This final secret is even kept from Romeo, who knows nothing of the plan and commits suicide before Juliet awakens in the Capulet tomb. Juliet follows by stabbing herself with a dagger. The play ends in terrible tragedy because of secrets that, if revealed sooner, may have saved the two young lovers' lives.