Dictionary.com defines emotions as: 1. an affective state of consciousness in which joy, sorrow, fear, hate, or the like, is experienced, as distinguished from cognitive and volitional states of consciousness. 2. any of the feelings of joy, sorrow, fear, hate, love, etc. 3. any strong agitation of the feelings actuated by experiencing love, hate, fear, etc., and usually accompanied by certain physiological changes, as increased heartbeat or respiration, and often overt manifestation, as crying or shaking.
I would like to add to it in that I believe emotions are the outward sign or display that reflects what my mind has told me to feel about a situation. They are my thoughts personified. My emotions let the other person know how I feel. Sometimes, my emotions are justifiable, and other times they are irrational to everyone else but me. My emotions show my perception of the situation. I said this to say that emotions are simply my response to my perception of my reality. Because we think--->we feel---->we behave. Our thoughts bring about emotions (what we feel), and our emotions sometimes, but not always, determine how we behave. I've learned through practice, practice, and more practice how to behave differently in spite of how I think (thoughts) and how I feel (emotions). It doesn't mean that I don't think or feel, it just means I think and feel but choose to behave differently.