Definition
What a company is worth on the stock market: its share price times its number of shares.
The story
A company with 1 billion shares at $100 each is worth $100 billion. Because the S&P 500 and Nasdaq-100 are weighted by market cap, the biggest companies move them the most. A bad day for a few giants can drag the whole index down.
Why markets watch it
It decides how much each company counts in the big indexes.
Connects to
We explain why it moves markets. What you do with it is your call. Commentary and education only. Not financial advice. All terms