What is defined as the internal emotional tone?

The correct answer is mood, as it specifically refers to the internal emotional tone that a person experiences over an extended period. Mood encompasses the overall emotional state that can influence feelings and perceptions, providing a more stable background against which daily experiences and emotions are interpreted.

Emotion, while closely related, typically refers to more immediate and intense responses to specific stimuli. Feelings are personal interpretations of emotions and can vary greatly from person to person based on individual experiences. Sentiment, on the other hand, often relates to a specific attitude or opinion, rather than the underlying emotional tone. Thus, mood is the most accurate term that encapsulates the sustained state of emotional tone that can affect behavior and decision-making.