Final answer:
The breaking of the unicorn's horn in Scene Seven symbolizes Laura's emotional vulnerability and the shattering of her illusions when confronted with reality in 'The Glass Menagerie.'
Step-by-step explanation:
The incident of the unicorn losing its horn in Scene Seven has a symbolic connection to the character of Laura in Tennessee Williams's play “The Glass Menagerie.” The unicorn, which is unique just like Laura with her own fragility and perceived oddities, becomes ordinary once it loses its distinctive horn. This corresponds with Laura's own transformation when she interacts with Jim, her gentleman caller, who temporarily makes her feel more normal and less self-conscious about her uniqueness, which is often symbolised by her limp. The breaking of the unicorn's horn signifies Laura's emotional exposure and the shattering of her illusions when she faces reality.