1. A small sac or cavity in a gland that secretes substances; the basic functional unit of a gland.
Usage: anatomy, biology
2. One of the small drupelets or seed-like segments that make up a berry, such as in a raspberry or blackberry.
Usage: botany

Examples

• The acinus is the smallest functional unit of a salivary gland.
• Each acinus in the pancreas produces digestive enzymes.
• The mammary gland contains numerous acini that produce milk.
• A raspberry is composed of many small acini clustered together.
• Under the microscope, the acini of the gland appeared as tiny rounded structures.