Mark

"Mark" is shorthand for the current market value assigned to a position, using the most recent price the market has actually traded at. Instead of valuing something at what you originally paid for it, marking it means updating its value to reflect what it would fetch right now if you had to sell it (or buy it back) this instant.

The practice this word comes from is called "mark-to-market." Brokers and clearing firms use it constantly: every open position in your account gets repriced, often continuously during the trading day and at minimum once at the close, so your account equity, buying power, and profit or loss reflect current prices rather than stale ones. If you bought a stock at 50 and it's now trading at 53, your position is "marked" at 53, and your unrealized gain of 3 points per share shows up in your account even though you haven't sold anything.

The nuance that trips people up is that a mark is not a guarantee of what you'll actually get if you trade. It's a snapshot based on the last trade price or the midpoint between the current bid and ask, and in a thinly traded stock, or one that's gapping around news, the mark can lag or diverge noticeably from the price you'd actually receive when your order fills. Marks can also matter beyond your own screen: a broker's mark on your positions determines whether you're meeting margin requirements, and a mismark (say, using a stale price in an illiquid name) can trigger a margin call that surprises you.

People also use "mark" loosely as a noun for the price itself, as in "the mark on that option is 2.35," meaning that's its currently quoted fair value, separate from where it last actually traded.