on Live Write Thrive:

Every person or character, at any given time, is in a particular mood. Generally, mood is a person’s state of mind, but it’s more than that. Mood can also describe the disposition of a collective of people, a certain time in history, or the ether of a place. We writers need to learn how to infuse mood into our fiction.

Regardless of what kind of mood we speak of, it’s always subjective. Ten people can be experiencing the same event at the same place and time, yet, depending on their perspective, their individual mood will differ.

We all know about moods and have a range of them we express and feel, whether we’re aware of them or not. We can sense others’ moods just as they can sense ours. The mood of the character should affect the way he perceives his environment, and expert writers will carefully choose words and imagery that act like a mirror to their emotions.