The author seems to know how the caged bird really feels and understands its struggle. He seems to show compassion for the caged animal through the way he tells of how it lives. Not only that, but the poem itself is titled 'Sympathy', which is kind of a synonym for 'compassionate'.
Many words and phrases were first written down in his plays. He contributed 1,700 words to the English language because he was the first author to write them down
