Final answer:
Market share is the proportion of the market that a firm captures.
Step-by-step explanation:
The proportion of the market that a firm captures is called market share.
Market share represents the percentage of total sales in the market that a particular firm holds. It is an important measure of a firm's performance and success in relation to its competitors. For example, if a firm has a market share of 20%, it means that it captures 20% of the total sales in the market.