tone

“Suggests an attitude toward the subject which is communicated by the words the author chooses. Part of the range of tone includes playful, somber, serious, casual, formal, ironic. Important because it designates the mood and effect of a work.” (The Purdue OWL)

“A writer's or speaker's attitude toward his or her readers and subject. Tone reflects the writer's stance: critical, playful, reasonable, ironic, and so on.” (Everyone's An Author, 1012)