Can a resting limit order be matched only by a market order, or also by an opposite side limit order?

External question — Personal Finance Stack Exchange Author: hanugm Original post: https://money.stackexchange.com/questions/169464 License: CC BY-SA 4.0 — https://creativecommons.org/licenses/by-sa/4.0/ Adaptation: HTML converted to plain text; contact email addresses removed. I am trying to understand this bolded statement about a limit order book: An LO is composed of a price level, a volume, and an indicator to buy or to sell the asset. Once an LO is posted by a trader, it rests (or sits) in the LOB until it is matched against an MO of the opposite side, or it is cancelled by the agent that posted it. If the LO is a buy LO, then it sits on the bid side of the LOB, and if it is a sell LO, then it sits on the ask side; Limit order books, Introduction, Lecture notes – HT 2024 by Fay¸cal Drissi My doubt is this: Why does it say “matched against a market order” only? Suppose there is already a resting sell limit order in the book at a certain price. If a new buy limit order arrives from the opposite side with a price that crosses or equals that ask price, then should they not match immediately? So is the above statement incomplete?

External answer — Personal Finance Stack Exchange Author: Bob Baerker Original post: https://money.stackexchange.com/a/169708 License: CC BY-SA 4.0 — https://creativecommons.org/licenses/by-sa/4.0/ Adaptation: HTML converted to plain text; contact email addresses removed. Your link provides an overcomplicated explanation. A market order has the same effect as a limit order (same price) if liquidity is present in the NBBO quote (USA). It makes no difference if the order is a limit or a market order if the liquidity exceeds the volume in the order. Suppose the quote is $50.00 x $50.25 with 1,000 shares on each side. If you place a market or limit buy order for 500 shares at $50.25, you'll be filled at that price. For more than 1,000 shares, for a market order, you'll get 1,000 shares at $50.25 and the remaining shares at whatever higher sell price(s) is/are on the book. A more than 1,000 share limit order - not AON (All Or Nothing) - will get 1,000 shares at $50.25 and the remainder will sit on the book until cancelled.