A soliloquy is the act of speaking by a single person, usually an actor in the theater.
A desolate area is unused, empty of life, deserted, and lonely.
Someone who is sullen possesses an ill humor, and so is generally gloomily silent and brooding much of the time.
A solitary person is by themselves; they are all alone with no one else around.
Solipsism is the contention that only the self exists and nothing else; this self-centered worldview can lead to extreme self-absorption and preoccupation with one's own feelings, needs, and desires.
A solo is a musical or other artistic performance that is done by only one person.
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