What Are SPX, NDX, DJIA, ES, NQ, and YM?

Match each family

SPX is commonly used for the S&P 500 index level, NDX for the Nasdaq-100, and DJIA for the Dow Jones Industrial Average. CME Group lists ES as E-mini S&P 500 futures, NQ as E-mini Nasdaq-100 futures, and YM as E-mini Dow futures. The complete futures symbol also identifies an expiration month and year; the front month changes over time.

Why the prices differ

A cash index is calculated from its constituents under index rules. A futures contract is traded by buyers and sellers and reflects the market's pricing of the index for a future settlement date, including financing and expected distributions. The difference between futures and the cash benchmark is often called the basis. It can change during the day.

Futures have their own trading schedule, and a contract can trade while the cash stock market is closed. A green overnight ES quote therefore does not prove the S&P 500 cash index has already risen in the regular session.

A practical reading check

Before comparing two screens, confirm that one is not showing futures while the other shows a cash index. Then compare the contract month, quote timestamp, session, data entitlement, and whether the figure is a last trade or a calculated index level. A stale cash close beside an active futures quote is not a like-for-like comparison.

Key takeaway

Use the symbol to identify the instrument first. Related futures and cash indexes are connected, but they are not interchangeable readings.