Definitions of capacity:

• noun:   a specified function

  Example: "He was employed in the capacity of director"

• noun:   the maximum production possible

  Example: "The plant is working at 80 per cent capacity"

• noun:   tolerance for alcohol

  Example: "He had drunk beyond his capacity"

• noun:   ability to perform or produce
• noun:   the power to learn or retain knowledge; in law, the ability to understand the facts and significance of your behavior
• noun:   (computer science) the amount of information (in bytes) that can be stored on a disk drive

  Example: "The capacity of a hard disk drive is usually expressed in megabytes"

• noun:   the amount that can be contained

  Example: "The gas tank has a capacity of 12 gallons"

• noun:   the susceptibility of something to a particular treatment
• noun:   an electrical phenomenon whereby an electric charge is stored