Affect often refers to the outward way in which a person
shows his/her feelings or emotions. Affect also refers to
the actual feelings or emotions that are attached to a
person's thoughts in addition to the way in which a person
demonstrates those feelings or emotions.

Affect is usually used in psychology and psychiatry as a
way to describe someone's feelings or emotions based on
the personís observed behaviors (most commonly the tone
of voice). Affect is usually described as different from
mood because mood is viewed as a more chronic
subjective emotional experience. 
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Affect can be described as blunted, which means that emotional expression is reduced
but not absent. Affect can be described as flat, which means that emotional expression is
almost totally absent or is totally absent. Affect can also be described as labile, which
means that it changes rapidly and easily. When affect is described as full-range, this
means that the person is displaying the normal range of affective expression as occurs
in everyday conversation. Affect can be described appropriate or inappropriate in a
certain situation. For example, flat affect is appropriate in the context of a close family
member passing away suddenly. However, flat affect can be inappropriate if the person
just discovered he/she won the lottery. Drug abuse is known to cause abnormal changes
in affect. Affect comes from the Latin word "affectus" meaning "state of mind."
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