ربا is an Arabic term that refers to usury or interest, which is the practice of charging excessive interest on loans. In many cultures, including Islamic teachings, ربا is considered unethical and is prohibited because it can lead to exploitation and financial hardship for borrowers. In Islamic finance, the prohibition of ربا is based on the belief that money should not generate money without effort or risk. Instead, financial transactions should be based on profit-sharing and risk-sharing principles, promoting fairness and social justice in economic dealings.