What is the theme of "Hamlet"?
To add to your previous list:
Ambition (Claudius, Hamlet, Polonius, Ophelia)
Family Relationships (Ophelia, Laertes, Polonius/ Hamlet, Gertrude, Claudius, King Hamlet)
Madness (Hamlet, Ophelia)
Appearances vs. Reality (Hamlet "acts" crazy; King Hamlet as the ghost, Claudius as innocent heir to throne, Gertrude as ally or innocent wife of a murderer, Rosencrantz and Guildenstern as friends to Hamlet)
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A short list:
Revenge - major theme - similar to Roman tragedies in which a principal character is driven by revenge.
Mortality - purpose in life (Hamlet's "to be or not to be" speech is the center of this. Ophelia's suicide also figures in this theme.
Friendship - Hamlet & Laertes, Hamlet & Ophelia, Rosencrantz & Guildenstern, etc.