What is the meaning of "nevermore" repeated by the raven? How does it change throughout the poem?

The line increases the tension of the poem as the speaker continues his story. At first, the word is used in a humorous way when the narrator asks the bird its name and it replies "nevermore." He thinks that is a strange name for a bird.As the bird continues to sit on the bust of Pallas, the Greek goddess of wisdom, the speaker is still not very affected by its presence because he thinks that bird will just leave the next day. But then the bird says "nevermore", making the speaker think the bird is telling him he will never leave.The speaker becomes a little concerned but simply thinks "nevermore" is the only word it knows. But then the tone changes. The speaker begins to think there is something more to its meaning and begins to wonder what "nevermore" really means.As he thinks, the narrator becomes more agitated, first when he realizes that in this world, he will see Lenore "nevermore". Finally, the speaker begins to think the bird is a messenger from the dead so he asks the bird if he will see Lenore in the next world. Of course, the reply is "nevermore". He repeats the question in several different ways and receives the same reply. Now the narrator is incensed. He tells the bird to leave and receives the reply "nevermore. Thus, the meaning of the word has gone from an odd name of a raven to a prophetic warning that he will never again see Lenore nor will he ever get rid of the bird. In the end, the speaker decides he will be happy, "nevermore."