Ambivalence is a state of having simultaneous, conflicting feelings toward a person or thing. Stated another way, ambivalence is the experience of having thoughts and emotions of both positive and negative valence toward someone or something. A common example of ambivalence is the feeling of both love and hatred for a person. The term also refers to situations where "mixed feelings" of a more general sort are experienced, or where a person experiences uncertainty or indecisiveness concerning something. The expressions "cold feet" and "sitting on the fence" are often used to describe the feeling of ambivalence.
The word "ambivalent" derives from the Latin prefix ambi, meaning "both" and valence which is derived from the Latin valentia, meaning "strength". It is common to use the word "ambivalent" to describe a lack of feelings one way or the other towards issues or circumstances. A more specific and conventionally accepted word to use in this case, however, would be "indifferent". A good way to remember proper usage is to remember that the prefix ambi means "both", so if you are "ambivalent", you have both positive and negative feelings towards something, or have feelings for both sides of an issue.
Ambivalence is experienced as psychologically unpleasant when the positive and negative aspects of a subject are both present in a person's mind at the same time. This state can lead to avoidance or procrastination, or to deliberate attempts to resolve the ambivalence. When the situation does not require a decision to be made, people experience less discomfort even when feeling ambivalent.