Jealousy is an envious resentment of someone or of their achievements. That can include resentment that someone can afford new clothes, new car, a tropical holiday or a larger house, while they cannot. It can also arise in families where one sibling thinks another is being treated in a more favourable way.
For most people jealousy comes with relationships. Ideally two people meet who are both self-confident, happy in their own skin and come together to share the great benefits of a relationship, without jealousy. Each will want the other to have what pleases them, having discussed any boundaries. They are two independent souls, enjoying life to the full, together. They put the other first.
The problems arise when one or both partners only feel whole because the other person fills their needs, and they are dependent upon each other for happiness, and so become possessive. They want the partner to fulfill their own needs, to give them self-esteem and confidence. They FEAR losing the partner and in effect chain the partner to them.
“You are mine” implies “ownership”. Jealousy is all about fear of loss, anger, insecurity, suspicion and controlling behaviour. A jealous partner may check e-mails, sms messages, pockets of clothes, and Facebook posts to attempt to confirm any suspicions. Having an innocent conversation with a member of the opposite sex may constitute unreasonable behaviour to the jealous mind. Having a coffee to discuss some topic of mutual interest may be perceived as an even greater threat.