Because Juliet is a religious teen, Shakespeare uses the word "sin."
The themes of the book include morality and womanhood. Cassy commits infanticide not because she wanted to do it but because she had no choice. She was a slave and that meant she did not have the capacity to raise the baby. Despite this, she still made her decision to kill the baby and that shows her 'moral weakness.'
The first one does NOT have an action. So it would be an adjective.