Mood

mood: this term has two distinct meanings in English Writing:

• The first is grammatical and refers to verbs and the speaker's attitude. The indicative mood is used only for factual sentences, (Joey eats too quickly.). The subjunctive mood is used for doubtful or conditional attitude, (If I were you I'd get another job. I'm obviously not you, so the sentence supposes a condition contrary to fact.) The imperative mood is used for commands (Shut that door!).
• The second meaning is literary  and indicates  the prevailing atmosphere or emotional aura of a work. Setting, tone, and events can affect mood, as well as diction. Syntax, is also a determiner of mood because sentence strength, length, and complexity affect pacing. In this usage mood is similar to tone and atmosphere

"So much of mankind's varied experience had passed there- so much had been suffered, and something too, enjoyed- that the very timber were oozy, as with the moisture of a heart. It was itself like a great human heart, with a life of its own, and full of rich and sombre reminiscences...It would be an omission, trifling indeed, but unpardonable, were we to forget the green moss that had long since gathered over the projections of the windows, and on the slopes of the roof; nor must we fail to direct the reader's eye to a crop, not of weeds, but flower-shrubs, which were growing aloft in the air not a great way from the chimney, in the nook between two gables. They were called Alice's Posies. The tradition was, that a certain Alice Pyncheon had flung up the seeds, in sport, and that the dust of the street and the decay of the roof gradually formed a kind of soil for them, out of which they grew, when Alice had long been in her grave."
                                                                                  -The House of the Seven Gables
                                                                                          by Nathaniel Hawthorne

Hawthorne is setting the mood here. He begins with a rather dark and almost depressed mood, but ends with a hopeful, border-line-bright mood. This combination of moods continues throughotu the novel. The mood is dark and depressed when Hepzibah or Clifford are present and is brighter and more cheery when Phoebe is present. When the two meet the mood is a mixture. Hawthorne uses this mood to communicate that the future has no place for the past, and that the old ways are dying, but there is hope, because there are better, brighter new ways.