Hormone/ˈhɔːrməʊn/ Definition 1 of 2Pro Tip 1/3Body Regulation Hormones manage vital functions like hunger, sleep, and stress. The hormone melatonin helps regulate your sleep cycle. Pro Tip 2/3Medical Context Often used in medical or biological discussions about health issues. Doctor suspects a hormone imbalance might be causing fatigue. Pro Tip 3/3Not Emotions Don't confuse hormonal effects with emotions; hormones impact, but don't equal feelings. She felt anxious, possibly due to stress hormones.