GLOSSARY // Orders & Execution
Bid
The bid is the highest price a buyer is currently posting for a stock, always paired with a size: a bid of $18.42 x 500 means someone will pay $18.42 for up to 500 shares right now. It is the price a market sell order receives.
The inside bid is only the top of the ladder. Beneath it, the book stacks lower bids at each price level, and the depth of that stack is what determines how far a burst of selling pushes price. When traders call a stock thick on the bid, they mean large resting buy interest that can absorb selling without the price dropping.
A stock is quoted $18.42 x $18.45 with 500 shares on the bid. A trader market-sells 800 shares: 500 fill at $18.42, exhausting that level, and the remaining 300 fill at the next bid down, $18.40. The quote is now $18.40 x $18.45.
Related terms
Educational only — not financial advice. Definitions simplified for clarity; markets are messier than definitions.