Segment
A business unit a company reports separately in its filings, with its own revenue and often its own profit.
A segment is a part of a company that is reported separately, usually because its products, customers or geography differ. Under US GAAP, companies disclose segment revenue and profit measures that management uses to run the business. Segment definitions can change, which affects comparisons over time.
On our site, segment figures come from the 10-K and 10-Q, with the reporting basis labeled. Check for restated prior-year figures before comparing growth.
Traders care because one company can contain a fast-growing unit and a declining one. Segment data often show where earnings growth really comes from.
Worked example (illustrative numbers, not real data): a company has two segments. Segment A has 3 billion dollars of revenue at a 20 percent margin, and segment B has 1 billion at 5 percent. Total operating income is 650 million. Segment A drives most of the profit, so a slowdown there matters more than one in segment B.