The term chalazion comes from a Greek word meaning small lump. A chalazion is an enlargement of an oil-producing gland in the eyelid called the meibomian gland. It forms when the gland opening becomes clogged with oil secretions. It is not caused by an infection from bacteria, and it is not cancerous.
What is the difference between a chalazion and a stye?
A chalazion is sometimes confused with a stye, which also appears as a lump on the eyelid. A stye is a red, sore lump near the edge of the eyelid caused by an infected eyelash follicle. Chalazia tend to develop farther from the edge of the eyelid than styes.