Endocrine describes the system in your body that makes hormones — chemical messengers that travel in the blood and tell organs what to do. The endocrine system includes glands such as the thyroid, the pituitary, and the adrenals. An endocrine gland secretes its hormone inside, into the bloodstream, rather than out through a tube. It is a science and medical word; you will meet it in biology class and at the doctor’s, not in everyday chat. Though actually, people sometimes just say “hormones” when they mean this whole system, which is close enough in daily talk. The contrasting idea is exocrine: those glands send their product out, like sweat or saliva, through a duct. You may also see endocrine as a noun meaning an endocrine gland, but the usual meeting is the adjective: endocrine system, endocrine disorder.