Epinephrine (INN) or adrenaline (BAN) is a hormone and a neurotransmitter. A neurotransmitter is a specific kind of hormone, released by neurons to regulate activity of target tissues (e.g. brain cells, muscle cells,...). The Latin roots ad-+renes and the Greek roots epi-+nephros both literally mean "on/to the kidney" (referring to the adrenal gland, which secretes epinephrine). Epinephrine is sometimes shortened to epi in medical jargon.