Who is queen mab?
It's not clear where Shakespeare got the idea for Queen Mab -- it may have been a Celtic goddess named Madb in Ireland and Mabb in Wales.
Mercutio describes Queen Mab as a tiny fairy who visits people as they sleep and gives them dreams. The dreams are of what the person would wish for, and his description suggests that these things are usually vices -- like violence, greed or lust.
In the play, Mercutio refers to Queen Mab to tell Romeo that his dreams of love are basically nonsense.
Queen Mab is a tiny fairy who enters the heads of dreamers and makes them believe that they have come up with ideas of their own so that they are justified in their cupidity. Mercutio's monologue plays upon the fancy of this little fairy as he cynically jests about Romeo's having fallen in love with Juliet.
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