Hordeolum, commonly known as a STYE, is an infection of the eyelid caused by bacteria. It is characterized by a red, swollen bump on the eyelid that may be painful or itchy. The term hordeolum is derived from the Greek word for 'little horde, ' referring to the small lump that appears on the eyelid. The medical term for a STYE is STY, which is a three-letter word, and the plural form is styes, which is a four-letter word.